JP3097863B2 - AlGaAs natural oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is partly based on a contract number given by the U.S. military.
DAAL 03 89-K-0008, approval number NSF ECD 89-4316
Issue 6, and NSF DMR 89 awarded by the National Science Association
Made with government support under -20538. The government has certain rights in this invention. This application was partially filed in 1990
Is a continuation of U.S. Patent Application No. 636313, filed December 31, 2012.

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of forming a high quality, high stability, small native oxide layer from an aluminum-containing III-V semiconductor material. More specifically, this method forms a native oxide layer by a method including wet thermal oxidation. Importantly, the thickness of the native oxide layer formed by this method is less than or equal to the thickness of the layer of aluminum-containing III-V material that is converted to oxide. Furthermore, the present invention forms natural oxides under conditions that prevent the formation of various other oxygen-rich compounds such as aluminum hydroxide oxides and aluminum suboxides. This increases the combined thickness of the native oxide layer and further causes general degradation in the electrical and physical properties of the semiconductor.

The present invention is directed to devices utilizing native oxide layers, including electrical and optoelectronic devices such as transistors, capacitors, waveguides, and more particularly lasers.

Finally, the invention relates to masking and passivation of semiconductors utilizing native oxides formed by practicing the invention.

Conventional technology Semiconductor device manufacturing is an important trend in semiconductor technology II
The use of group IV materials can be mentioned. Silicon (S
The use of i) is widespread in this area.
III-V compounds such as aAs have been the subject of much research due to the significant advantages they provide.
For example, III-V compounds generally have large band gaps, large electron mobilities and the potential to generate more light, but this property is unique as an electrical and optical property.

Despite these properties, III-V semiconductor technology has not been successfully developed at the speed and level of silicon-based technology. Although the primary incentive factor for this purpose does not allow for the formation of the required thickness of oxide layer on the III-V semiconductor, this thickness requires the required surface conditions and the electrical requirements for the practical application. The characteristics are represented. In this regard, oxides can perform various functions in a practical and consistent manner without causing degradation and distortion due to excessive oxide thickness. Examples of these features include: acting as a mask during device fabrication, inerting the surface, isolating from other devices (insulating isolation as opposed to junction isolation). ), To operate the various device structures in isolation, and to provide electrical isolation for multilevel metallization. Therefore, having a stable oxide layer of high quality with appropriate physical properties and appropriate thickness is essential to the successful development of III-V semiconductor technology.

Unlike III-V semiconductors, high quality oxides (SiO ₂ ) by silicon-based materials, for example by reacting silicon crystals with steam in the form of steam.
Can be easily formed. Silicon-based integrated circuit technology has greatly affected the ability of silicon to form high quality silicon oxide. Further, the oxide is a native oxide with respect to the deposited oxide layer. Although native oxides are preferred over deposited oxides, they are monolithic with crystals, potential mismatch in dielectric properties, and oxide-to-base interface bonding such as lifting and cracking. It is because various problems related to can be prevented. Furthermore, the process of deposition is more complex overall and more expensive than growing native oxides which are easy to use commercially.

Attempts to form high quality native oxide layers on III-V semiconductors by a successful adaptation method to silicon have been unexpected. These results are based on the fact that the behavior of III-V materials largely depends on the behavior of the individual constituents of III-V, but under certain conditions this behavior is the required result. Not compatible with For example, one of the easiest thermal oxidation techniques considered to be among the easiest, and very good for silicon, is GaAs
Cannot be well adapted to group III-V materials such as This is because gallium (Ga) and arsenic (As) have different oxidation rates, and because AS ₂ O ₃ and AS ₂ O ₅ produced by conventional methods are variable: once formed These tend to boil the substrate rather than stabilize as part of the oxide layer.

Other approaches have been developed to prevent the formation of volatile components at low temperatures, such as room temperature, and to form a native oxide layer directly from the surface of a III-V semiconductor, with most occurring. ing. These technologies include photos of ozone, simultaneous O ₂ , electron beam exposure, and electron hole pairs.
Use of excitation (in GaAs), (such as N ₂ O) reactive oxidants, photochemical excitation of the vapor molecules, the application of water to O _2, the O ₂ by hot filament excitation or Tesla discharge, O ₂ And the use of exposure to fast moving beams of plasma excitation and atomic oxidation. The disadvantages of these techniques are, in addition to the overall complexity that makes them impractical for widespread use, despite the increased rate of formation of the first few monolayers of oxide (plasma oxidation and atomic oxidation). Hundreds to thousands of Angstroms ({10,000} = 1 micron, μm) by eliminating as much as possible exposure to high speed motion beams
Is generally ineffective for high-speed growth layers having a thickness in the range Furthermore, these oxidation reactions are often incomplete, with Ga and As not in the apparently highest oxidation state. The oxides formed are usually imperfect Ga or As, which impairs the quality of the oxide.

Specific examples of these methods are included in US Pat. No. 3,859,178, in which the oxide converts the GaAs layer to pH.
Is grown on the surface of GaAs by immersion in an electrolyzed water bath of concentrated hydrogen peroxide (H ₂ O ₂ ) less than 6.

U.S. Pat. No. 4,347,867 describes a method of growing an oxide layer on InGaAs by using a growth chamber, which is evacuated to form an oxygen plasma therein. Water vapor enters this chamber to facilitate the growth process.

U.S. Patent No. 3890169 concerns a method for forming an oxide on the GaAs in the form of using H ₂ O ₂ as the electrolyte. The oxides thus formed are more stable and less conductive to impurities and dopants, but these impurities and dopants are usually dried in oxygen at 250 ° C. for 2 hours, and then dried at 600 ° C. for 30 hours. Diffusion treatment by annealing for minutes is applied.

Although double oxidation technique in U.S. Patent No. 3,914,465 are described, thereby native oxide is immersed in an aqueous H ₂ O ₂ solution in a pH of 1.5-3.5, the pH after this 6-8 It is grown on the GaAs by the second oxidation of the aqueous H ₂ O _2.

"Semiconductor Science and Technology" by H. Barbe et al., 3, page 8
53-858 (1988) describes growing a thin oxide layer on GaAs in methanol with various waters without using an external voltage. JPContour et al., “Japan Journal of Applied Physics,” Vol. 27, No. pp. L167-L169 (198
(February 8) reported the preparation of a surface oxide on a GaAs substrate by heating the substrate from 250 ° C to 350 ° C with air. Similarly, "Applied Physics Letter" Vol.26,
No.4, pp.180-181 (February 15, 1975) has a temperature of 350 ° C and 450 ° C.
The growth of an oxide film on GaAs by thermal oxidation at 500 ° C. and 500 ° C. is described. “Applied Physics Letter”, Vol.29, No.1, pp.56
At -58 (January 1, 1976), a method for forming an oxide film on GaAs by plasma oxidation using oxygen plasma was developed.
Two dry treatments have been reported. Due to the complexity of these technologies, as well as their physical properties and thickness, they are all related to difficulties in operation with Ga and As, but the method of forming this oxide requires materials that can be more easily oxidized III- Includes stacking or implanting on group V. Aluminum (Al) and aluminum-containing compounds are examples of such materials. These particular materials are particularly adaptable, and it is known that aluminum is a Group III element and can be more easily oxidized than other elements commonly found in Groups III-V.

An example of a method of oxidation utilizing the presence of aluminum or aluminum-containing compounds is U.S. Pat.
No. 634, which first deposits a thin layer of Al on a GaAs substrate, for example by evaporation. The Al layer is oxidized by plasma oxidation. Y. Gao et al. Described low temperature technology in “Journal of Applied Physics”, 87, (11), pp. 7148-7151 (January 1, 1990). ; Deposition of Al follows. A
l reacts and forms an oxide layer until oxygen disappears.

CWWilmsen et al., "Thin Solid Films", 51, pp. 93-98 (197
8) reports a method in which a metal such as Al is embedded in a III-V group base. M. Hirose et al. “Physical solids”
(A) 45, pp. K175-K177 (1978) reports an oxidation process for GaAs. The oxidizing gas near the surface substrate reacts with the Al molecular beam to form Al ₂ O ₃ . Finally,
U.S. Pat.Nos. 4216036 and 4216036 and European Patent Application No. 00088898 describe the production of oxides by thermal oxidation of AlAs and AlGaAs layers.
The GaAs and AlGaAs layers are grown epitaxially on GaAs. Oxidation occurs in the mixing gas 80% O ₂ and 20% N, further low temperature, for example for use in a 70 ° C. -130 ° C. occurs as there is water vapor; oxides produced by this method, however It is believed to be aluminum arsenic oxide and / or aluminum hydroxide oxide. These types of oxygen-rich aluminum compounds do not have the physical properties required for semiconductor applications. Furthermore, the presence of said compounds, even in appropriate amounts, is detrimental to semiconductor structures. In addition, in conjunction with the presence of hydroxylation, the thickness of the final oxide layer increases, which is 80% higher than the thickness of the original AlAs epi layer. For practical applications and device constructions, this magnitude of layer spread is entirely impractical due to the fact that this distorts and distorts the configuration of the device to an unacceptable level, and the poor interdependent size and shape. is there. These drawbacks are particularly fragile when the semiconductor device is an optoelectronic device such as a laser, and the light output efficiency and lifetime are increased by the proper crystal size and shape so that the various layers occur during device fabrication. It depends. Briefly, prior art methods, due to the presence of materials such as aluminum, are complicated to use on a large scale, or the rollers that contain significant hydroxide and / or have a thickness that is excessive Occurs inside. Oxides produced by these methods have physical and electrical properties, but have poor electrical properties such as high leakage and poor physical properties. In this regard, oxides formed by conventional methods are non-uniform in density, continuous, and lack stability, which results in lifting, cracking,
Out-diffusion occurs; devices made with oxides generated by these methods are prone to degraded performance under normal conditions of use and for unacceptably short periods of time in air. These undesired consequences and detrimental effects render these methods unusable for large-scale applications required as commercial equipment. Thus, semiconductor technology is III-V
Various methods of forming group semiconductor materials have been proposed,
It has been found that there is a continuing need for a method of growing an improved high quality native oxide on an aluminum-containing III-V semiconductor material, and in particular the thickness of the native oxide depends on the semiconductor material from which it is formed. Less than or equal to the thickness of
Further, it is desirable that the method be simple and cost-effective, and that the production of native oxide be controlled and repeated.

SUMMARY OF THE INVENTION The development of a new method for forming high quality native oxides on aluminum-containing III-V semiconductors is presented. The native oxide grown in this way has an appropriate range of thickness at the changed portion, and is further superior in physical and electrical properties as compared with an oxide formed by a known method.

In particular, the thickness of the native oxide layer formed by the method of the present invention is less than or equal to the thickness of the portion of the aluminum-containing material forming it. The native oxide layer thus formed does not deteriorate, for example, under normal use and under atmospheric conditions. It is slower and more stable than oxide layers formed by prior art methods and devices. In addition, the native oxides formed according to the present invention exhibit superior operating characteristics over all other currently used oxide films. For example, native oxides formed according to the present invention have excellent metallization and dielectric properties. Native oxides formed by the method of the present invention have been used in optoelectronic devices, particularly lasers, which can withstand shrinkage of the oxide layer, but exhibit excessive expansion in the oxide layer. It is done violently. Lasers manufactured in this way have a long lifetime and a high output before the lifetime.

According to the invention, the native oxide is aluminum-containing
A method is provided for forming on a surface of a III-V semiconductor material. The method comprises subjecting the aluminum-containing group semiconductor material to a water-containing environment and a temperature of at least about 375 ° C. to convert a portion of the aluminum-containing group III-V semiconductor material to native oxide. The native oxide has the feature that the thickness of the native oxide is approximately equal to or less than the thickness of the corresponding portion of the aluminum-containing III-V semiconductor where the thickness is varied.

Further, according to the present invention, there is provided a semiconductor device using the natural oxide thus formed. Devices with particular applicability in this regard include electrical and optoelectronic devices such as transistors, capacitors, waveguides, and more particularly lasers.

Further, according to the present invention, masking and passivation of a semiconductor using a native oxide formed by the method are described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a yellow gap Al _x G after oxidizing according to the invention in nitrogen and steam at 400 ° C. for 3 hours.
Shows a thin plate of disordered red-gap AlAs-GaAs superlattice (SL1) disc surrounded by a _1-x As (x is about 0.8). The top row of the SL board (indicating a rough steel alloy) shows cracked edges that have been converted to native oxide 24 μm deep beyond the crystal edge (indicated by a small horizontal arrow) according to the invention. ing.
The thickness of the oxide is the same as the thickness of the corresponding portion of the original SL1 changed by 24 μm. The oxide is apparently transparent.

FIG. 2 is placed in nitrogen and steam at 400 ° C. for 1 hour,
AlAs-GaAs superlattice (SL1) after oxidation according to the present invention
Is shown. The oxide that can be converted to the edge region of the SL board is 3 μm. (Indicated by small horizontal arrows). 3μ
The thickness of the oxide in the m region is the same as the thickness of the corresponding portion of the changed SL.

FIG. 3 is placed in nitrogen and steam at 400 ° C. for 4 hours,
AlAs-GaAs superlattice (SL2) after oxidation according to the present invention
Is shown. SL2 is an alloy with a smaller scale than SL1, and the oxide is 2-3 μm at the edge of the SL board. The thickness of the oxide in the 2-3 μm region is the same as the thickness of the corresponding portion of SL2. The long-term slow rate of change for SL1 in FIGS. 1 and 2 is due to the fine alloy scale of SL2.

FIG. 4 shows the effect of a room temperature (300 ° Kelvin, K) laser with a photographic pump of the red gap SL1 disk of FIG. 2 oxidized according to the present invention. The sample is compressed on a soft copper heat sink under a diamond window.

FIG. 5 (a) is a scanning electron microscope photomicrograph showing the quantum well heterostructure (QWH): the left side of the figure shows the QWH masked with SiO ₂ ; the right side shows the QWH with a GaAs cap. The GaAs has been removed and the exposed crystals have been oxidized according to the invention in nitrogen and water vapor at 400 ° C. for 3 hours. FIG. 5B shows the QWH after the oxide on the right side has been selectively removed. FIG. 5 (b)
The hatched arrow indicates the crystallographic plane defined by native oxide on the Al _x Ga _1-x As (x is about 0.8) confinement layer in this layer.

FIG. 6A shows the left masking region (SiO 2) of the QWH of FIG.
To the contact in the region right to have a natural oxide formed by the present invention in FIG. 6 (b); _{the 2} contact the current-to-voltage on the GaAs cap layer (shows I-V) characteristics of removal) This shows an IV characteristic. FIG. 6A shows pn conduction, and FIG. 6B shows an open circuit (I ≒ O).

FIG. 7 shows the spectral behavior and power versus current (LI) of a QWH laser with native oxide formed according to the invention at 20 mA, mA, 30 mA and 40 mA.

FIG. 8 shows the operation of the high power laser of the QWH laser of FIG. 5 incorporating the native oxide formed according to the present invention. Not destroyed up to 100 mW / W or more.

9 shows an _{Al X Ga 1-X As-} GaAs (X is about 0.8) QWH surface of multiple over striped contact area made using a native oxide formed by the present invention over the crystal in the photo micrographs I have. FIG. 9 (a) shows the natural state where the QWH was placed in nitrogen and water vapor at 400 ° C. for 3 hours on the upper confinement layer of Al _x Ga _1-x As (x is about 0.8) not masked by the contact layer. The oxide is shown. FIG. 9 (b) shows all surfaces metallized with titanium-platinum-gold (Ti-Pt-Au).

FIGS. 10 (a) and 10 (b) show that the distance between centers is 7 μm.
10 is a near field (NF) emission pattern and a far field (FF) emission pattern of the 10 element multiple stripe QWH laser array shown in FIG. 100m
When the power is half at A, all angles are 0.6 ° (Fig. 10 (b))
Indicates that the stripe is double.

FIG. 11 shows the operation of a continuous wave (CW) room temperature (300 K) laser for the 10 emitter QWH double array of FIGS. 9 and 10 with the center having a 5 .mu.m wide stripe over 7 .mu.m. I have. The output power per surface is approximately 300 mW.
At the insertion, the appearance of the spectrum of this diode indicates that the output power is 10 mW (115 mA).

FIG. 12 shows 10 Emitter natural-oxide double stripes
₁ shows an Al _x Ga _1-x GaAs QWH laser array. The width of the stripe is the same as the width of the array in FIG. 11 (5 μm), but above the center of 10 μm as shown in the insert. Output power exceeding 400 mW per surface is obtained.

FIG. 13 shows a 1.05 μm Al _x G mask in which a stripe is masked on the surface (top) of the crystal after zinc (Zn) is diffused.
An a _1-x As-GaAs superlattice shows a cross section inclined at a small angle. This masking stripe is made of a native oxide formed according to the present invention. The lower part of the sloped section is the area that is not masked by the oxide but has an irregular superlattice; this irregular area is an alternating masked portion of native oxide, with the superlattice remaining. You can see that

FIG. 14 shows Al _x Ga _1-x As-Al _y Ga _1-y As-Al _z Ga _1-z AsQWH
(X is about 0.8, y is about 0.25, z is about 0.06) shows a fractured cross section of a small plate sample. The native oxide formed by the process of the present invention is shown by removing the substrate and etching the tapered holes through all layers (stop at the oxide). As shown in region A, the natural oxide layer is clear enough to transmit light and further show fouling. The upper confinement layer is indicated by region B. The QWH waveguide and the upper and lower confinement layers are indicated by region C. The entire QWH is indicated by region D.

FIG. 15 shows a photo-pump type continuous wave (C) of the annealed QWH of FIG. 14 including a native oxide formed by the method of the present invention.
W) Operation of a room temperature (300 K) laser. For comparison, FIG. 15B shows impurity-induced laser irregularities (IILP)
3 shows the operation of a non-masked bare sample pulsed pump laser modified by R.S. Each sample was annealed at 575 ° C. for 1 hour in a Zn diffusion ampoule.

FIG. 16 shows the buried heterostructure (BH) (using stain) on the right and left sides after performing Si diffusion at 850 ° C. for 6.5 hours (indicated by the letter “n”) and performing impurity-induced laser disordering on the left and right sides. 2 shows an image of a scanning electron microscope (SEM). According to the present invention, oxidation of the upper confinement layer at 400 ° C. for 3 hours in the atmosphere of nitrogen and water vapor is performed. The Si diffusion cuts under the edge of the GaAs cap, which creates a contact area of about 5.5 μm and an active area of about 7 μm (about 6 μm masking stripe). The formation of native oxide by the method of the present invention takes place at the surface of the exposed high-gap Al _x Ga _1-x As confinement layer and extends to the edge of the GaAs cap (as indicated by the two downward arrows).

FIG. 17 shows a continuous wave (CW) room temperature (300 K) output (single-plane) power versus current (L
-I) and the spectrum. The laser diode has an activation region with a width of 3 μm (the width of the activation region is 7 μm in the case of the laser of FIG. 16). The laser threshold (250 μm long diode) is 5 mA, and single mode works well at 7 mA (wavelength is about 819881). The narrowing and "ringing" of the spectrum begins at about 2 mA and the top of the curve at the inset (3 mA) is blurred.

FIG. 18 shows the near-field (NF) and far-field (FF) emission patterns of an active region IILDQWH having a width of 3 μm, which were formed by the present invention under 12 mA continuous wave (CW) excitation. Painted by native oxide. The width of the near field (NF) pattern shown in (a) is approximately
It is half of the maximum power of 3.4 μm. The angle of the far field (FF) shown in (b) is diffracted at a half power of 20.4 °.

FIG. 19 is an image photograph of Nomarski, which is oxidized in the atmospheric state as shown in FIG. 19A, and is a natural oxide layer formed by the present invention as shown in FIG. 19B. In this example, an AlAs-GaAs heterostructure having the following structure was placed for 100 days. The sample oxidized in air (a) is largely characteristic of hydrolysis in air, and the sample (b) oxidized by the method of the invention is covered with a smooth "blue" oxide, Furthermore, it is not affected by the aging process.

FIG. 20 (a) is a scanning electron microscope (SEM) image (cross section without stain) of the sample (a) of FIG. 19 having grooves and aged (after 100 days). Fig. 20
Fig. 1 (b) shows a groove with aging (after 100 days).
It is a SEM image of 9 samples (b). Sample (a) is chemically eroded to a depth of 1 μm (indicated by a vertical arrow) and has streaks. Conversely, sample (b) has a thickness of 0.
The area under the native oxide of less than 1 μm is smooth.
This thickness is less than the thickness of the relevant portion of the heterostructure converted to oxide.

FIG. 21 shows the state of the secondary ion spectrometer (SIMS) after aging the samples (a) and (b) of FIG. 20 for 80 days. According to the SEG image of FIG. 20, the Ga deficiency is approximately 1 μm in sample (a), which is not clear in sample (b). Further according to FIG. 20, FIG. 21 shows that the chemical erosion is about 1 μm for sample (a).
m; a chemical erosion at this depth is not apparent in sample (b).

Embodiments The present invention provides a method of forming a high quality native oxide from a III-V semiconductor material, wherein the thickness of the native oxide is changed to a native oxide. It is equal to or less than the thickness of the part. The native oxides formed in accordance with the present invention have particular utility in the manufacture of electrical and optoelectronic activation devices, including lasers such as capacitors, transistors, and even stripe guide lasers and surface emitters. The activation region typically has a slightly mismatched emission energy wavelength, as defined by the quantum well structure. An example of such a device has a first quantum well formed, for example, of InGaAs instead of a second quantum well formed, for example, of GaAs. The native oxide formed by the method of the present invention is further used to define various shapes or patterns on the surface of the III-V semiconductor material to form many different arrangements.

The method of the present invention finds particular use in forming native oxides from aluminum-containing III-V semiconductor materials. While the scope of this invention is not related to any theory explaining good results, the invention is theorized by forming native oxides in a manner that prevents hydration and / or degradation of oxygen-rich aluminum compounds. However, it is believed that these compounds increase the thickness of the native oxide layer formed by previously known thermal oxidation techniques with respect to the thickness of the relevant portion of the aluminum-containing material. In another aspect, the present invention provides that the aluminum oxide and / or aluminum hydroxide (referred to herein as the anhydrous aluminum compound) is fully in the anhydrous form, thereby reducing the thickness of the native oxide thus formed. It is conceivable that the thickness of the relevant portion of the aluminum-containing III-V material that is converted to oxide is less than or equal to the thickness.

Regarding the oxygen-rich aluminum compound already mentioned,
These include compounds having e.g. Al0, Al ₂ O, the Al ₂ O _2. Those compounds that adversely affect semiconductor properties and stability are referred to herein as aluminum suboxides.

It is believed that when using the known wet thermal oxidation method, it is considered to form an undesired one. Further, the above-mentioned hydrated compound which deteriorates the quality of the native oxide and increases the thickness thereof includes water as described below. Including aluminum oxide and aluminum oxide hydrate.

With respect to aluminum hydroxide, a well-known crystalline form generally includes three trihydroxides in the form of Al (OH) ₃ , which are conventionally known as gibbsite (hydrazirite in Europe). hydragillite), which is called bayerite, norstrandite. The adverse effect of these aluminum hydroxides on semiconductor applications relates to the triply hydroxylation state.

With respect to aluminum oxides, these are formed from intermediate or transitional forms of aluminum oxide, Al ₂ O ₃ . These intermediate forms, each of which are unsuitable for semiconductor practical purposes, are generally represented as: η-Al ₂ O ₃ , χ-Al ₂ O ₃ , δ-Al ₂ O ₃ , θ-Al ₂ O ₃ , κ-Al
₂ O ₃ , ν-Al ₂ O ₃ . These intermediate forms of aluminum oxide fall between the structural range of pure anhydrous aluminum oxide and the form of aluminum hydroxide. Thus, some of these intermediate forms can be formed from hydrates of the form Al ₂ O ₃ .nH ₂ O (0 <n <0.6). Hydrates formed from these intermediate aluminum oxides are called aluminum oxide hydrates. Further, it is considered that, for example, as the degree of hydration of trihydrate to monohydrate increases, the degree of spread of the thickness of the native oxide layer increases.

One technique for determining the magnitude of hydration in the oxide layer is to measure the index of refraction (indicated by "n"), and the prior art relates to the dielectric constant. In general, the higher the refractive index, the greater the degree of hydration of the oxide layer, and the more unstable this oxide is for practical semiconductor applications. For example, the refractive index of a hydrated aluminum compound such as aluminum oxide hydrate generally ranges from about 2.0 to about 11.0. In comparison, the refractive index of the anhydrous oxide is generally in the range of less than about 2.0. For example, Ga formed by oxidizing gas plasma
The refractive index of the dehydrated film of As oxide is about 1.78 to about 1.87 as measured using conventional polarization techniques; the refractive index of dearsenic arsenic (Al ₂ O ₃ ) is about 1.93. In general, anhydrous aluminum oxide and aluminum hydroxide oxide have a refractive index of about
Less than 2.0.

In addition to forming this native oxide to prevent degradation of the formation of hydratable / oxygen-rich aluminum compounds as described above, the thickness of the aluminum-containing material that can be converted to native oxide by the practice of this invention is approximately Aluminum oxide and / or hydrated aluminum oxide are converted to anhydrous form to obtain native oxides of the same or smaller thickness and having the physical and electrical essential properties required for practical semiconductor applications. It is considered that the present invention forms a natural oxide so that a large amount can be obtained at the same time.

In this regard, the thickness of the native oxide, whose thickness is approximately equal to or less than the thickness of the aluminum-containing material, is, for the purposes of the present invention, the ratio of the native oxide thickness to the aluminum-containing material thickness. Can be measured. As can be seen from the present invention, this ratio is in the range of about 0.6 to about 1.1 (showing about 40% native oxide layer shrinkage and about 10% expansion compared to the aluminum-containing material). This does not adversely affect the physical properties of the native oxide.

For the anhydrous form of aluminum oxide, α-Al ₂ O
₃ and γ-Al ₂ O ₃ . Understanding that stoichiometrically there is only one oxide of aluminum, Al ₂ O ₃ , and that this oxide is polymorphic is important in evaluating this invention: Although there are various crystalline forms and different structures, most of these are sub-standard as far as beneficial semiconductor-related electrical and physical properties are concerned, such as the aforementioned intermediate aluminum oxides. In general, the form of aluminum oxide that defines the highest degree of parameters required for practical applications of semiconductors is the anhydrous form, including α-Al ₂ O ₃ and γ-Al ₂ O ₃ .

For example, α-Al ₂ O ₃ has a well-examined close-closed lattice structure, better hardness, stability, resistance to wear and erosion, chemical inertness (insoluble in water) Properties, including non-reactivity to water), outstanding electrical properties (such as dielectric properties), good thermal shock resistance, dimensional stability, and mechanical strength.

For aluminum hydroxide oxide, AlO (O
It contains two well-known crystalline phases of the form H), which phases are conventionally indicated by diaspores and boehms.

It is believed that the native oxide formed according to the present invention is formed more like the anhydrous form of aluminum oxide and / or aluminum hydroxide oxide than deteriorating the hydratable and / or oxygen-rich aluminum compound,
It is believed that this situation is manifested by the thickness of the native oxide formed according to the invention being approximately equal to or less than the thickness of the aluminum-containing material.

The molar volume is an indicator in this regard. That is, the fact that the thickness of the native oxide of the present invention is approximately equal to or less than the thickness of the corresponding portion of the aluminum-containing material which is converted to the native oxide means that the present invention relates to an aluminum-containing III-V semiconductor. It is believed to indicate that it is formed from a native oxide compound having a molar volume approximately equal to or less than the molar volume of the material.

The molar volume is expressed in the following form: molar volume = molecular weight / density AlAs (considered aluminum-containing III-V material in this invention), α-Al ₂ O ₃ , and γ-Al ₂ O ₃ ( The anhydrous form of aluminum oxide as shown in this invention), diaspore (aluminum hydroxide oxide as shown in this invention), gibbsite (aluminum hydroxide as shown in this invention), aluminum mono- and trihydrate (Hydrated aluminum oxide as shown in this invention) is represented in Table 1 below: As can be seen in Table 1, the molar volumes of aluminum oxide, α and γ-Al ₂ O ₃ , aluminum hydroxide oxide are Al
As small as, or less than, the molar volume shown in As, indicating that the oxide is formed from the AlAs that embody the present invention, and the thickness of the native oxide is
And less than or equal to the thickness of the relevant part, and is primarily constituted in anhydrous form of a dehydrated aluminum compound, ie aluminum oxide and / or aluminum hydroxide oxide. Conversely, when the thickness of the native oxide formed from AlAs is greater than the corresponding portion of oxidized AlAs--in this case, early attempts, such as the methods implemented in U.S. Pat. Produce native oxide-which is primarily composed of compounds having a larger molar volume than AlAs, such as aluminum monohydrate, aluminum trihydrate, gibbsite, and aluminum hydroxide. Conceivable.

Like aluminum, gallium is also formed from oxides and Ga ₂ O ₃ has a number of crystalline forms; these crystalline variants are α-Ga ₂ O ₃ , β-Ga ₂ O ₃ , γ −Ga ₂ O ₃ , δ−Ga ₂ O ₃ ,
It is represented by ε-Ga ₂ O ₃ . Of these, β-Ga ₂ O ₃ is the most stable and most suitable for use in semiconductors. Furthermore, under appropriate conditions, aluminum oxide such as α-Al ₂ O ₃ and gallium oxide such as β-Ga ₂ O ₃ form a solid solution and
Forms a compound of aAlO ₃ . In an embodiment of the invention, the native oxide is formed from a III-V semiconductor material; for example, AlGaAs, AlInP, AlGaP, AlGaAsP, AlGaAsSb, InAl.
Aluminum-containing III-V semiconductors such as GaP, InAlGaAs are preferred.

In an embodiment of the invention, the aluminum-containing III-V
The semiconductor material overlies the surface of an aluminum-free III-V semiconductor material such as, for example, GaAs, GaP, GaAsSb, InGaP, InGaAs. When the thickness of the aluminum-containing layer is not so great and impedes diffusion of the required oxidant reactant through the aluminum-containing layer, the conversion of the aluminum-containing layer to a native oxide layer is reduced to the aluminum-free III-V group. Substantially terminates at the interface of, or if less than about 30% of the aluminum is in a given layer or interface layer, for example, x is Al _x Ga _1-x
In materials such as As it is about 0.3. The diffusion effect that ultimately stops the oxidation reaction is usually a factor when the thickness of the aluminum-containing material is greater than about 10,000 °.

The method of the present invention exposes the aluminum-containing III-V semiconductor material in an environment that preferably contains water vapor but contains water. In the preferred practice of embodiments of the present invention, the water vapor is with an inert gas such as nitrogen. These water vapors are preferably in nitrogen or other inert gas which is substantially saturated with water. While an inert gas environment containing water is preferred, it is not necessary in a flow state. During this flow, the speed is at least about 0.1 per hour.
It must be 5 standard cubic feet (scfh), but is preferably about 1.0-3.0 scfh, especially 1.5.

In the practice of the present invention, the temperature is at least 375 ° C. First of all, it is not necessary to exceed a specific time to form the native oxide, but certain implementations in this regard have been particularly implemented in aluminum-containing III such as Al _x Ga _1-x As where x is greater than about 0.7. It is preferably applied to a group V semiconductor material.

Thus, in the first embodiment, the temperature used was about 37
Preferably from 5 ° C to about 600 ° C, especially from about 390 ° C to about 500 ° C, and more preferably from about 400 ° C to about 450 ° C, and when exposed to an environment containing water, exposed for about 0.1 hours to 6.0 hours. Is preferred. A more preferred time for this first embodiment is 1.0 to 5.9 hours; a more preferred time is 2.0
From time to 4.0 hours. The most preferred time for the first embodiment is 3.0 hours.

In a second embodiment of the invention relating to rapid heat treatment,
Temperatures ranging from about 600 ° C to about 1000 ° C have been employed.
According to this second good aspect, the temperature employed was about 65
It ranges from 0 ° C. to about 1000 ° C., more preferably from about 700 ° C. to about 900 ° C., and most preferably about 800 ° C.

In the practice of the second embodiment of the present invention, exposure to a water-containing environment depends on whether the material is self-capping under the conditions of use. If not, this exposure time is about 120
Preferably, it is seconds. A more preferred time for this second embodiment is from about 5 seconds to about 90 seconds; even more preferred is from about 10 seconds to about 60 seconds, and most preferred for this second embodiment is from about 15 seconds to about 90 seconds. 30 seconds.

The preferred time in the practice of the second embodiment of the present invention is reduced in view of the fact that certain III-V materials, such as arsenic, have a tendency to evaporate at higher temperatures. Shorter exposure times of non-self-capping material are preferred to prevent and minimize any losses.

In the practice of the present invention, particularly in the practice of the second embodiment described above, the material to be oxidized is first exposed to the aforementioned temperature, or for about one second as in a conventional annealing furnace or oven. The following is preferred, but heating is performed from a low temperature, for example, room temperature (about 20 ° C. to 25 ° C.), to these temperatures in a heating device which can reach these temperatures in about 2 seconds or less.

In each case, this temperature is kept constant in the practice of the invention. Thus, this temperature varies up and down, for example, in the range described above. It is believed that these temperature ranges prevent the formation of hydrated aluminum compounds and / or aluminum suboxides that adversely affect the final oxide and use of the semiconductor for this purpose. At the same time, it is believed that these temperature ranges prevent the formation of anhydrous forms of aluminum oxide such as α-Al ₂ O ₃ and / or aluminum hydroxide oxide such as diaspore.

Other treatments occur after exposing the aluminum-containing III-V material to a water-containing environment without deleteriously affecting native oxides. Thus, the native oxide and its structure, while continuously heating at a different temperature, equal to or higher than the temperature used to form the oxide,
Dry in a watery environment. An inert gas is added to the structure containing the native oxide to facilitate this drying. For example, flowing steam at about 400 ° C. to about 450 ° C.
In a nitrogen (or other inert gas) system, the flow of steam into the system is stopped after, for example, 0.25 hours; the flow of nitrogen gas, however, lasts for example 2 hours. The temperature of the flowing nitrogen system is the same as the temperature used during the formation of the oxide, or this temperature is for example
It changes up and down between 450 ° C and 500 ° C.

Another treatment that occurs after oxide formation and that does not adversely affect the quality of the native oxide is annealing. This annealing is performed in a "dry" state, i.e., without water, as is conventionally done for III-V semiconductor materials.
The dry state in this regard usually uses an N ₂ gas environment. Annealing is further performed by pressurizing the material used in the annealing that tends to evaporate in the hot state. Thus, the native oxide-containing structure is annealed in an ampoule that selectively includes arsenic or phosphorus pressurization; the former involves the use of arsenic-containing III-V semiconductor materials (such as AlGaAs). Commonly used, the latter being used for phosphorus-containing III-V semiconductor materials (such as InGaP). Annealing is generally about 600 ° C to 8 in all cases.
The reaction is carried out at a temperature of 50 ° C., usually about 0.25 hours to about 4 hours.
It is preferably carried out at a high temperature, for example 850 ° C., for a time.

The following example is provided to illustrate the scope of the present invention.
The present invention is not limited thereby, as these examples are given for illustrative purposes only.

Example 1 Oxidation of Al _X Ga _1-X As-AlAs-GaAs quantum well heterostructures and superlattices AlAs-GaAs superlattices (SLs) were described by RDDupuis et al. Minutes "(Physical Society, London, 1979), P1-9, and MJ Ludowise
By the metal-organic chemical vapor deposition technique according to J. Appl. Phys., 58R31 (1985). Some SLs are each about 1 micron (μm) thick. The superlattice, denoted SL1, has an AlAs barrier with a LB of about 150 ° in size and a GaAs well of about 45 ° in width LZ. The superlattice denoted by SL2 has LB (AlAs) of about 70 ° and LB (GaAs) of about 30 °. Although superlattices have special properties, such as size quantization, they are further regarded as Al _x Ga _1-x As alloys which are relatively “coarse” or non-stochastic. In this example, SL1 is twice as coarse as SL2. SL1 and SL2 have a (100) surface and are described by DGDeppe et al. In J. Appl. Phy., 64, R93 (1988
Year), and WDLaidig et al. Appl. Phy. Lett., 38,776 (1
981) Impurity-induced layer disordering (IILD) by diffusion of (Zn) from ZnAs ₂ at 575 ° C. for 0.5 hour as described by
In a random or fine scale alloy.

SLs are masked with a SiO ₂ disk with a diameter of about 37 μm. The disk was deposited by chemical vapor deposition and the center was patterned (by standard photolithography) into a square array of about 76 μm. After removing the Zn diffusion and masking SiO ₂ , the red gap SL (approximately 37 μm in diameter) is distributed in a uniform array, similar to the removal of the crystal substrate (by standard methods of mechanical lapping and wet chemical etching). Smooth yellow gap Al with disk
_x Ga _1-x As small plate (about 1μm thick) is N. Holonyak
Other Appl, Phys. Lett., 39, 102 (1981). The alloys of the "fine" scale (yellow) and the "coarse" scale (red) are all in one sample, but this sample has been oxidized by the method of the present invention: the sample is maintained at 95 ° C. Heated in a furnace at 400 ° C. for 3 hours in an environment of H ₂ O steam obtained through N ₂ carrier gas (flow rate is approximately 1.5 scfh) through a ₂ O bubble. The samples thus obtained by this method form native oxides with smooth and glossy surfaces, but they are glossier than before oxidation.
The characteristics of this surface are that it is a free, compact and compact oxide of hydroxide oxide alumina, and that most of the native oxide components are formed like anhydrous aluminum oxide like α-Al ₂ O ₃ It is that you are.

The cracked portion of SL1 oxidized according to the present invention is shown in FIG. The top edge of the SL board having a diameter of 37 μm is cracked, and the SL sample (board) is arranged so as to be exposed to the oxidation treatment of the present invention. The lower row of disks is unbroken and the surface (front and back) is exposed to the oxidation treatment of the present invention. Converting a cracked SL disk to native oxide as shown in FIG. 1 is performed at a depth of about 24 μm as measured from the edge of the SL (indicated by a small horizontal arrow). The thickness of this oxide is the same as the thickness of the cracked and exposed SL. No increase in the thickness of the native oxide layer is observed. The lower row of disks shows the peripheral oxidation. After oxidation according to the method of the invention, the upper row of disks is solid;
Whole is close to almost _{clear, Al x Ga 1-x As} (x is approximately 0.8) Materials by IILD the appearance column at the bottom of and disk yellow is red (SL1 having an oxidized surface).

By reducing the time of the oxidation process from 3 hours to 1 hour (all other parameters being the same), the oxide at the end of the disk of SL1 is about 3 μm measured from the end of S1 as shown in FIG. At depth (indicated by a small horizontal arrow). This depth (thickness) is the same as the depth (thickness) of the corresponding portion of the SL disk converted to oxide. There is no spread or increase in this oxide compared to the original SL thickness. In FIG. 1, the time is 3 hours, whereas in FIG. 3, SL2 (L
B + LZ is about 100Å) The oxidation time is 3 hours. Oxidation of the edge of the disk of SL2, which is a finer-scale alloy than SL1, takes a long oxidation time, and takes place at a depth of 2-3 μm as measured from the edge of SL. The 2-3 μm oxidation depth is about the same as the original SL thickness converted to oxide. No increase or spread to the depth (thickness) of the oxide is seen. IIL of Al _x Ga _1-x As material of yellow gap (x is about 0.7)
Alloy D is also oxidized, but not extensively; oxidation requires little attention except for shiny surfaces. (AlA
The difference in oxidization of the s) _x (GaAs) _1-x alloys is seen when going from a coarser scale to a finer scale with less “slow” changing composition in a random alloy. But,
In all cases, the thickness of the oxide formed by the method of the present invention is about the same as the thickness of the relevant portion of the alloy that is converted to oxide.

1 to 3 show that the oxide formed on (AlAs) _x (GaAs) _1-x SLs has large anisotropy. Oxidation on the layer is "slower" than following the layer, and is equal when the approach is initiated or when the Sl scale is fine. This is shown in Figure 3 (LB + LZ of SL2 is almost 100
Å) It can be found by comparing with FIG. 1 (LB + LZ of SL1).

The high quality of the oxide formed by the method of the present invention has been demonstrated by a photopump laser. FIG. 4 shows FIG.
Shows the operation of a photopump-type laser on one of the SL1 disks inside (sealed end) of the sample; this sample is heated and compressed in annealed copper under a diamond window according to conventional methods. The laser operation of this SL sample (300 K) uses the loss due to oxidation of several layers on both sides of the red gap SL disk, and furthermore, the difference in crystal and doping (heavy p-type edge) The periphery has non-uniformity. It is believed that these results are due, at least in part, to the fact that the thickness of the native oxide formed is about the same as the thickness of that portion of the crystal that is converted to oxide. That is, since the thickness of the thus formed native oxide is the same as that of the SL layer where the laser structure has almost no distortion, high-performance operation is possible.

Example 2 Single stripe Al _x Ga _1-x As made of native oxide
GaAs quantum well heterostructure laser Gain-guided oxide-Striped quantum well heterostructure (QWH) lasers were investigated for use of native oxides according to the invention. It can be seen that these devices formed by simple processing have outstanding operating characteristics, but these characteristics are that the native oxide properties and the native oxide thickness are the same as the corresponding parts of the crystal. It is directly based; thus, the structure of the laser is free of distortion or strain as occurs when the thickness of the oxidized portion increases.

The epitaxial layers of these lasers are referred to as Du in Example 1
It is formed on an n-type (100) GaAs substrate by metal organic chemical vapor deposition (MOCVD) as described by Puis et al. The low confinement layer of Al _0.8 Ga _0.2 As is the first GaAs
It is formed after the buffer layer. The activation region of the QWH is then formed; this activation region is approximately 400 mm thick.
GaAs quantum wells (QW) are symmetrically constituted by Al _0.25 Ga _0.75 As waveguide layers on both sides. Finally, a confinement layer above p-type Al _0.8 Ga _0.2 As is formed on the top of the QWH to a thickness of about 9000 °. The QWH is capped by a fully doped p-type GaAs contact layer having a total thickness of about 800 °.

The diode is formed by chemical vapor deposition (CVD) of SiO ₂ on the surface of the crystal at about 1000 °. Using standard photolithography and plasma etching techniques, a 10 μm wide stripe of SiO ₂ is formed on the surface of the wafer for masking. Crystal
Ga in areas not protected by the SiO ₂ masking stripes
To remove the As contact layer _{H 2 SO 4: H 2 O} : H 2 O (1: 8: 80) is etched in. Except for the stripe region with a width of 10 μm, this exposes the confinement layer above Al _x Ga _{1 -x} As (x is approximately 0.8). The native oxide is formed from the fully exposed aluminum-containing upper confinement layer by the method of the present invention. QWH crystal is about 95
It is heated at 400 ° C. for 3 hours in H ₂ O vapor formed by passing a N ₂ carrier gas (rate about 1.4 scfh) through a H ₂ O bubble maintained at 0 ° C. Exposed Al _x Ga _1-x A
s (x is about 0.8) is converted to native oxide at about 1500 °. The oxide thus obtained by this method has a thickness of about 1000-1500 °, which is less than the thickness of the corresponding part of the exposed upper confinement layer, and is also clear and transparent ( It is uniform blue (when blue is produced by optical effects). After oxidation, the SiO ₂ masking layer is removed by conventional plasma etching (CF ₄ and 4% O ₂ ). The native oxide is stabilized by plasma removal of the SiO ₂ layer.

FIG. 5 shows a cross section of the crystal before removing the SiO ₂ masking layer. The vertical arrows in FIG. 5A indicate the thickness of the SiO ₂ layer (left) and the thickness of the native oxide layer (right). FIG. 5B shows a cross section in which the native oxide (right side) has been removed by etching in a KOH-K ₃ Fe (CN) ₆ mixed solution. A set of vertical arrows in FIG. 5 (b) indicate the position of the oxide before removal. FIG. 5 shows that the oxidation method of the present invention is somewhat related to crystal orientation. For example, FIG. 5 shows that the oxide has cut off the masking stripe of SiO ₂ and the lower part of the GaAs contact layer, and the crystal is formed on the Al _x Ga _{1 -x} As (x is about 0.8) confinement layer. Tend to form biological steps. This shows a small hatched arrow in FIG. In connection with crystal orientation, native oxide has been shown to be compatible with the underlying structure, which means that bonding problems at the interface are minimized or eliminated.

After removal of the SiO ₂ masking stripe, the crystal is sealed in a shallow Zn diffusion (ZnAs ₂ , 25 min, 540 ° C.) ampoule to increase GaAs stripe contact doping. Crystal is exposed Ga
Titanium-Platinum-Gold (Ti
-Pt-Au). This metallization is performed on this native oxide better than on oxides or other dielectrics according to the prior art methods, which metallization often strips. After p-type side metallization, the crystal is tin-plated (up to 100 μm) from the substrate and germanium-gold-nickel-gold (Ge-Au-Ni-Au) on the n-type side.
The metallization is performed. A wafer is created in the crevices in the Fabry-Perot bar and the saw cut stripe contact is attached to the copper heat sink with indium (In) to operate as a continuous wave (CW) laser at room temperature, ie, 300 ° K. . A similar saw cut without contact stripes is provided to examine the operation of oxide blocking.

FIG. 6A shows the current-voltage (I-) of a diode made on a QWH crystal in the GaAs contact stripe region.
V) Characteristic; FIG. 6 (b) shows an open-body diode (with the same scale) that results when there is no contact stripe (ie, when the saw cut contacts the native oxide on the crystal). ).

The high quality of these laser diodes is explained by their operating characteristics (continuous wave at 300 K). The diode (having a cavity length of approximately 500 μm) shows a threshold according to the spectrum curves of (a) 20 mA, (b) 30 mA, and (c) 40 mA as shown in FIG. The corresponding points on the power versus current (LI) curve are shown in the insert in FIG. The power versus current characteristics are steep and exhibit a cleaved-coupled cavity diode. This allows the oxide to ripple (ie, jagged) the crystal surface due to its sensitivity to crystal orientation (related), unlike those formed by prior art methods, and to provide some natural distributed feedback. Is presented. As the diode exhibits a threshold (FIG. 7), there is some tendency for multiple mode operation (spectral "ringing"). The spectrum curve (b) of FIG. 7 is narrow but free of ringing, and at a higher current (c) of 40 mA, the single mode is dominant above the threshold as shown in FIG.

The quality of these recessed oxides, the quality of single-stripe diodes, and the attachment of metallization to native oxide allows for easy indium attachment to copper heatsinks on the sides of the oxide, but this results in a QWH
Heat sinking is very effective in the immediate vicinity of the activation area. FIG. 8 shows the operation of a possible high power continuous wave laser. 100mW per surface before destruction
Is over.

In addition to the high performance exhibited by the oxide laser diode of this example, one of the more salient features is its ease of manufacture. CVD SiO ₂ is used in the mask to obtain a 10 μm wide GaAs contact stripe, which can be easily removed by photolithography, which frees the manufacture of oxide stripe lasers for any CVD process .

Example 3 Multiple stripes of natural oxide Al _x Ga _1-x As-Ga
As quantum well heterostructure laser As shown in FIG. 2, the more prominent feature of the native Al _x Ga _1-x As (x is 0.7 or more) oxide formed by the method of the present invention is that the metallization is good. (Which can be used for heat sinking of the equipment), and through a normal photolithography process, this native oxide allows the foreign and potentially mismatched dielectric material (such as SiO ₂ Si ₃ N ₄ ) )
A diagram for the geometry of the device is provided without depositing In this example, a simple process and a high performance
10 stripe Al _x Ga _1-x As quantum well heterostructure (QW
By configuring the laser of (H), natural Al _x Ga _{1 -x} As (x
Are as described above). The difference in the oxidation state of Al _x Ga _{1 -x} As (x is about 0.7 or more) compared to GaAs with respect to oxide formation is fairly small, and the current contact metallization is easily performed.

The epitaxial layers for these coupled stripe QWH lasers are formed on an n-type (100) GaAs substrate by metal organic chemical vapor deposition (MOCVD) as described in the article referenced by Dupuis et al. In Example 1. GaAs
The buffer layer has an n-type Al _0.8 Ga _0.2 As lower confinement layer formed first. An activation layer of QWH is then formed, and on both sides an Al _0.25 Ga _0.75 As waveguide layer (undoped, about 1000 mm thick) having a thickness of 400 mm.
It consists of s quantum well (QWH). Finally, the p-type
Al _0.8 Ga _0.2 As upper confinement layer is approximately 90
It is formed up to a thickness of 00 °. The entire QWH is capped by a p-type GaAs contact layer approximately 800 ° thick and heavily doped.

The GaAs contact layer has been removed by the method of the present invention and the upper confinement layer has been accessed to convert a portion of the layer to native oxide. The GaAs contact layer is not easily oxidized,
Furthermore, when the native oxide is composed of part of the upper confinement layer, it can be used directly as a mask (and also a contact layer). The standard photoengraving method is 10 μm with a width of 2 μm and a width of 5 μm.
Used to mask GaAs stripes (distance between centers is 7 μm). Like GaAs between stripes, GaAs between stripes (2 μm in width) is H ₂ SO ₄ : H ₂
Removed by O: H ₂ O (1: 8: 80). As a result, Al _x Ga _1-x A
The upper confinement layer of s (x is about 0.8) is exposed to oxidation according to the invention. QWH in a bubble of H ₂ O held at 95 ° C
Heated at 400 ° C. for 3 hours in H ₂ O steam obtained by passing N ₂ carrier gas (flow rate is about 1.4 scfh).

After oxidation, the crystals of QWH are shown in FIG. 5
The μm GaAs contact stripes are shiny (silver) and insensitive to oxidation. Including the 2 μm area between the GaAs stripes, the remainder of the crystal is covered by native oxide formed by the method of the present invention. This native oxide is clear, transparent and uniform; the color appears blue due to optical effects and the thickness is 1000-1500Å. The thickness of some of the upper confined layers converted to native oxide is also about
1000-1500−1. The thickness of such native oxide is less than the corresponding thickness of the aluminum-containing upper confinement layer.

FIG. 9 (b) shows the QWH after metallization with titanium-platinum-gold (Ti-Pt-Au) over the entire surface by the conventional technique. Prior to metallization, the crystal is Zn diffused to a shallow depth (ZnAs ₂ , 540 ° C. for 25 minutes) to improve contact on the GaAs stripe. No special masking is required for this procedure. The crystal is thinned to about 100 μm, metallized on a germanium-gold-nickel-gold (Ge-Au-Ni-Au) substrate, and placed in the grooves of the Fabry-Perot resonator stripes. Is 10
Saw cut in individual striped dice. These are attached to copper (Cu) using indium (In) on the sides of the stripe for heat sinking and electrical testing. The current-voltage (IV) characteristic of the diode has a small resistance value (almost 2 ohms,
Ω). This indicates that the GaAs contact layer is not affected by the oxidation method of the present invention. Furthermore, the leakage current is small, indicating that the native oxide has good current blocking.

The near-field and far-field radiation patterns for one of these devices are shown in FIG. This device is mounted on the junction at the top and the threshold is about 95 mAW. FIG. 10A shows a near-field image taken with a Si metal oxide semiconductor (MOS) camera using a continuous wave (CW) laser having a current of 100 mA. Eight of the ten emitters in the array continue to this current. The other two stripes can be seen on a more centimeter scale, but not without saturating the camera with the eight stronger emitters. The near-field image shown in FIG. 10A shows that the effective current is limited by the stripe of the native oxide.

FIG. 10 (b) shows a far field pattern of the same device as that used in FIG. 10 (a). Radiation is 25mmf /
Collected with a 0.95 lens, an image is created on an array of linear charge-coupled devices. The twin lobe pattern is a characteristic of the π-phase shift coupling between the emitters.

The lower trace in FIG. 10B shows a far field pattern at 100 mACW corresponding to the near field pattern shown in FIG. The left peak is dominant because non-uniform current is injected and there is non-uniform operation near the threshold. 6.8mm peak interval is 7μm
This is consistent with the calculated value of 6.9 ° for the remote emitter (wavelength 8470 °). All corners (FAHP) at half the power of the left peak at 100 mA are 0.6 °, indicating that the full aperture of the array has a 68 μm coupling (above the 7 μm center). There are 10 stripes with a width of 5 μm). When the current is increased, the carrier injection and the intensity of the emitter become uniform, and as a result, the 145 m of FIG.
The twin lobe far field pattern shown at A results.
The FAHP in both lobes of the upper trace was 1.1 °, indicating weaker coupling of the array and / or reduced aperture of about 44 μm (seven emitters). The peaks separated by 5.0 ° indicate that the phase shift between the emitters is slightly smaller (transverse gain effect), the array of uncoupled emitters with a width of 5 μm has a far field divergence of 10 ° FAHP, Roughly shown here is a couple of arrayed robe widths of 10
Twice as large.

The simplicity of these coupled stripe configurations and the good heating of the GaAs contact stripes through the recessed native oxide have resulted in significant power output. The power versus current situation for one of the diodes (continuous wave at 300 K) is shown in FIG. Insertion part
It shows the output spectrum at 10mW (one side), which is
Drive current is higher from 8456Å (1.466eV) 8.479Å
It shifts to the dominant mode at (1.462 eV), but shows an additional 100 mW of output power (single plane). This corresponds to a temperature increase of about 10 ° C when the band filling is large.

Since the gain guide laser of this example is connected for a long distance, the spacing between the emitters is further increased and the heat sinking is further improved. FIG. 12 shows the power versus current situation for ten stripe lasers similar to that used in FIG. 11, but the spacing between the stripes has been increased to 5 μm (see insert in FIG. 12). . Since the power supply is limited, the operation of this laser ends at 400mW (single surface; 2
Amps, A).

Example 4 Impurity-Induced Laser Masked with a Natural Oxide Disordered Al _x Ga _{1 -x} As Quantum Well Heterostructure In this example, the invention is used to make Al _x Ga _{1 -x} As (X> 0.7).
We are investigating the masking ability of native oxides formed on silicon. Especially in this example, Zn diffusion, bare Al _x G
The focus is on impurity guiding layers which make the situation between a _1-x As-GaAs superlattice (SL) or quantum well heterostructure (QWH) crystal irregular, the SL or QWH being the method of the present invention. Masking is performed by the natural oxide formed by the method described above. In the latter case (masked native oxide), the quantum well (QH) and superlattice (SL) layers are shown to be retained.

The superlattice (SL) and quantum well heterostructures (QWH) used in this example were made of (100) GaAs by metal organic chemical vapor deposition as described in Dupuis et al., Cited in Example 1. Formed on the substrate. In the case of the SL crystal (Crystal # 1), a GaAs buffer layer is formed, followed by an undoped Al _0.8 Ga _0.2 As lower confinement layer (approximately 0.1 μm thick). Next 40
GaAs wells (about 110 ° Lz) and 41 Al _0.4 Ga _0.6 A
It consists of an s-barrier (about 150 mm LB). The overall thickness of the SL is approximately 1.05 μm. Finally 1000Å Al _0.8 Ga _0.2 As
The upper confinement layer is formed above SL. This structure is capped with 3,000 mm of GaAs layer.

For QWH crystal, MOCVD QWH (Crystal # 2)
The first part is an n-type GaAs buffer layer (with a thickness of about
0.5 μm), followed by an intermediate layer of n-type Al _0.25 Ga _0.75 As. The lower confinement layer of n-type Al _0.8 Ga _0.2 As is then formed. After this, there is a well activation region, which is an Al _0.06 Ga _0.94 As (QW) quantum well with a thickness of about 200
Two undoped Al _0.25 Ga _0.75 As
It is sandwiched between waveguide (WG) layers. Finally, p-type Al _0.8 G
a _0.2 As Upper confinement layer (about 9000 mm thick) is formed above the activation region. The entire QWH useful for laser diode fabrication is capped by a heavily doped p-type GaAs contact layer having a thickness of about 800 °.

The GaAs cap layer in both SL and QWH has been removed and the upper AlGaAs confinement layer (x about 0.8) has been exposed to the oxidation method according to the present invention. The presence of Ga in the oxide layer and at the interface of the native oxide semiconductor does not adversely affect the structure of the native oxide, but it has the same structure in which gallium oxide and aluminum compounds have the same crystalline form, and This is because Al ₂ O ₃ and Ga ₂ O ₃ form a solid solution in the entire structural range represented by the upper confinement layers of SL and QWH. Oxidation of AlGa1-As is performed according to the present invention.
By heating the sample at 400 ° C. for 3 hours in an environment of H ₂ O water vapor obtained by passing a N ₂ carrier gas (flow rate about 1.5 scfh) with H ₂ O foam held at 5 ° C. Done.

A photoresist stripe pattern (20 μm stripe with 50 μm center) is formed on top of the native oxide to provide selective Zn diffusion and irregularities in the layer within the SL sample (Crystal # 1). NH ₄ F: HF
When the (7: 1) buffer HF aqueous solution is used, native oxide is selectively removed in the stripe pattern as shown in FIG. The sample was cleaned in an aqueous NH ₄ OH solution and further ZnAs ₂ (10 m
g) is immediately sealed in the ampoule. The shallow wrap of the SL sample after diffusion is shown in FIG. Formed by the practice of the present invention, FIG.
Al _0.4 Ga _0.6 As-GaAs SL underneath from the diffusion of Zn and from the mixing of layers that occur in the region where the oxide is removed, with a native oxide mask named
(Having an overall thickness of 1.05 μm) can be seen to remain under the native oxide mask, but otherwise mixed.

In the case of a QWH wafer (Crystal # 2), the two samples are sealed in an ampoule with ZnAs ₂ for simultaneous heating and further IILD diffusion (575 ° C. for 1 hour). One of the samples has a native oxide masking layer according to the method of the invention and the other sample is a QWH with a GaAs cap. Selective Zn-IIL of SL in FIG. 13
As with D, the QWH sample has an oxide formed by the method of the present invention but is not irregular. In comparison, a mixed layer occurs as a QWH comparative sample, which has no native oxide masking layer; (determined by photoluminescence measurements).

QWH, either masked or unmasked
The sample is primarily used for photoluminescence measurements using conventional techniques up to a thickness of approximately 2 mils. Next, the remaining portion of the substrate and the GaAs buffer material were H ₂
It is removed by performing wet chemical etching in SO ₄ : H ₂ O: H ₂ O (4: 1: 1) and performing selective etching. A photomicrograph of the portion where the oxide of QWH (crystal # 2) is masked is shown in FIG. The photomicrograph in Figure 14 shows "rough etching" of the oxide layer
At a given point, taken by light transmitted through the thinned QWH crystal, this graph is represented by the characteristics of the QWH and native oxides formed by the method of the present invention.

With reference to FIG. 14, region A of the photomicrograph indicates that the quality of this native oxide is good, ie, it is clear and transparent and was formed by oxidation of the AlAs-GaAsSL crystal of FIG. Same as oxide. In fact, the oxide is very clear and dust particles on the surface of this oxide are visible. Residuals indicate that various layers of QWH material are deep in the crystal. In region B, the oxide and upper QWH confinement layer (Al _0.8
Ga _0.2 As) is visible, and the color is yellow due to the optical effect. In region C, like the upper and lower confinement layers, the addition of the waveguide and the QW activation layer looks orange due to the optical effect. Finally, in region D,
The entire thickness of the QWH looks red (also due to optical effects). Some of the buffer layer that has not been completely removed at the edge of the crystal is also seen in region D (x is about 0.25).

Further, cracked samples have been examined by photoluminescence (PL) to determine the performance of native oxides formed to mask crystals from Zn-IILD according to the present invention. Masked native oxide and unmasked samples exposed simultaneously to Zn and As at 575 ° C for 1 hour
Heatsinked in copper under diamonds for photopumping with an Ar ⁺ laser (5145Å). The resulting photoluminescence spectrum (laser operation)
See Figure 15.

FIG. 15 (a) shows that the laser wavelength (continuous operation, 300 ° K) for the native oxide masking sample occurs at 7992 ° (1.565 eV); for the pulse-excited non-masking sample of FIG. Has been shifted to 7140Å (1.736 eV). In FIG. 15B, in the laser operation of the unmasked QWH crystal (Zn-ILLD), the shift to approximately 170 meV corresponds to the bulk-crystal waveguide region (x is about
This is consistent with what is expected for Al _x Ga _1-x As QW mixed within 0.25). This indicates that the non-masked sample is mixed (the energy shift is 170 meV) while the native oxide masked sample of FIG. Further, although the QW band filling is clear for the sample of FIG.
The state of the bulk crystal is clear for the IILD sample of (b). Interestingly, Figure 15 (a)
The native oxide masking sample (a) occurs through the transparent oxide, indicating that the native oxide formed by this method is of high quality.

Example 5 Natural oxide buried heterostructure Al _x Ga _1-x As-GaAs quantum well laser with low threshold irregularity Appl Phys. Lett., 38776 (1981) by WDLaidig et al.
J. Appl. Phys., 64, R by DGDeppe et al.
93, (1988), Impurity Induced Layer Irregularity Method (IILD)
DG Depp et al., J. Appl. Phys., 58, 4515 (1985), which is used to fabricate ultra-high performance buried heterostructure (BH) quantum well heterostructure (QWH). Various dopants and diffusion techniques are irregular, including:
Used to produce BH lasers: (1) Si solid source diffusion, (2) Si embedding and annealing,
(3) Diffusion of Ge from steam, (4) Diffusion of Zn from steam (5) Diffusion of SiO from Al reduced SiO ₂ , (6) Diffusion of Si from Al reduced Si / Si ₃ N ₄ by rapid thermal annealing, ( 7) Diffusion of Si from laser-melted Si ₃ N ₄ . Many of the techniques resulting from the formation of these diffusion sources and highly conductive layers on the crystal surface are presumably based on the formation of dopant-crystal alloys. This conductive layer is a source of leakage, which increases the threshold current of the laser. Indeed, under certain conditions, the dopant crystal alloy method is very difficult, and deeper burying is necessary to activate the leakage region and lower the threshold operation.

This example illustrates a "self-aligned" process,
The surface of the crystal is converted to a high quality current blocking native oxide by the method of the present invention. It has been found that the oxide thus formed activates the surface,
Reduced leakage current, low threshold irregular BH Al _x G
a Improve the formation of _1-x As-GaAs quantum well heterostructure lasers.

The QWH laser crystal used in this example was formed on an n-type substrate by metal organic chemical vapor deposition (MOCVD) as described by Dupuis et al. The formation of GaAs having a thickness of about 0.5 μm and about 1 μm
This is performed with an n-type buffer of Al _0.25 Ga _0.75 As having a thickness of This is followed by the following formation: approximately 1.1 μm
Thickness of Al _0.77 Ga _0.23 As n type lower confinement layer; almost
2000 mm thick Al _0.25 Ga _0.75 As undoped waveguide region; Al 1.1 Ga (11000 mm) thick Al _0.8 Ga _0.2 As p-type upper confinement layer; Al _0.1 Ga thick p-type GaAs
s cap. At the center of the waveguide, an undoped Al _0.06 Ga _0.94 As quantum well about 200 ° thick is formed.

The laser diode manufacturing process begins with shallow Zn diffusion over the entire surface in an empty quartz ampoule at 540 ° C for 30 minutes. The shallow p ⁺ layer formed by diffusion controls lateral Si diffusion at the crystal surface (below the masking region) in the processing step. After Zn diffusion, the crystal is 72
About 0 ° C deposited by conventional chemical vapor deposition (CVD)
Encapsulated in 1000Å of Si ₃ N ₄ . The Si ₃ N ₄ has been patterned with photoresist and further etched with CF ₄ plasma within the width of two stripes. The photoresist is removed with a residual Si ₃ N ₄ stripe which acts as a mask during the chemical etching of the GaAs contact layer with H ₂ SO ₄ : H ₂ O ₂ : H ₂ O (1: 8: 80). This etching exposes the high gap Al _0.8 Ga _0.2 As upper confinement layer. After the stripe is written, almost 3
00Å thick Si layer (500 ℃ CVD) and almost 1700Å thick SiO ₂
A cap layer (400 ° C. CVD) has been deposited. The crystal is sealed in an empty quartz ampoule,
Annealed with excess As at 850 ° C for 6.5 hours. Si diffusion is performed by annealing at high temperature, and IILD is performed outside the GaAs contact stripe.

The encapsulation is removed by etching with CF ₄ plasma and the crystals are oxidized according to the invention as follows: The crystals are placed in an open tube furnace at 400 ° C. for 3 hours (through H ₂ O at 95 ° C.) foamy N ₂ carrier gas). This results in an exposed upper confinement layer of approximately 2000 ° beyond the edge of the GaAs contact stripe. The thickness of the formed oxide layer is approximately the same as the thickness of that portion of the upper confinement layer. No oxide is formed on the GaAs contact stripe due to the selectivity of the oxidation process. Only the native oxide in the aluminum mixture is formed in the self-aligned contact stripe. After oxidation according to the method of the present invention, the wafer is sealed in a ZnAs ₂ source ampoule and annealed at 540 ° C. for 30 minutes to form a contact region, ie, a shallow, highly doped p-type region. The sample is conventionally wrapped to a thickness of about 5 mils, stripped, metallized with titanium-gold (Ti-Au) on the p-type side, and germanium-nickel-gold (Ge- Ni-Au) has been metallized;
This sample is interrupted in a bar approximately 250 μm in length.

FIG. 16 shows a scanning electron microscope (SEM) image for a burned cross section of a 6-μm-stripe laser structure after the oxidation method of the present invention to form a Si-II LD and a self-line contact stripe. FIG. 16 shows, by way of reference, that the impurity-inducing layer randomly mixes the waveguide region with the surrounding confinement layer (outside the GaAs contact region) to provide a current confinement pn junction. Side diffusion is approximately 5.5μm in contact and approximately 7μm wide
In the activation region of Similarly, for a diode treated with a 4 μm stripe, the contact area is about 2.5 μm.
m, the width of the active region is approximately 3 μm. High gaps outside the GaAs contact stripe by the method of the present invention
Oxidation of the Al _x Ga _1-x As region is due to the formation of high quality current blocking native oxide on the crystal surface. Oxide figure
At 16 the GaAs contact stripe has been formed up to the end of the GaAs contact stripe indicated by a vertical arrow not marked by a "notch" at the end of the stripe. This has occurred in self-line areas that have the potential for leakage by converting these areas to native oxide. The native oxide is substantially thicker than shown in FIG. 16, but
This is because K ₃ Fe (CN) ₆ -KOH which burned is used to dissolve the hetero layer matched the oxide.

Laser diodes fabricated using native oxides formed according to the present invention are pulsed between 3.5 mA and 6 mA (for 3 μm stripes) and between 7.5 mA and 9.5 mA as tested at the probe station. There is a threshold. FIG. 17 shows a continuous wave (CW) light pulse versus current (LI) curve for a 3 .mu.m stripe diode mounted on the p-side by an indium-coated (In-coated) copper (Cu) heat sink. . The continuous wave (CW) threshold at room temperature (300 K) is 5 mA for this device (uncoated surface). The stripe data shown by this diode initially has a narrow spectrum and then "rings" at about 2 mA, which corresponds to good carrier and optical composition and low edge leakage. doing. The laser generated in the 8198 モ ー ド single longitudinal mode works well at 7mA and is increased to at least 20mA. This laser diode has an external differential quantum efficiency of 53% (increased to about 10mW)
31mW / before output power causes catastrophic damage
It is not larger than the surface. For powers greater than 10 mW, an increase in the LI plot curvature indicates that the heating effect becomes significant. However, this phenomenon is based on the considerably higher forward resistance of the diode (Rs is about 20Ω), but not on the fact that this native oxide produces heat dissipation. Thus, the native oxide formed by the method of the present invention acts as a good current-blocking layer for striped laser diode operation. These diodes exhibit sharp turn-on characteristics and have no noticeable leakage through the oxide.

The unmounted laser diode of FIG. 17 has a pulse threshold of 4.5 mA. Other diodes also have a very small increase in pulsed (unmounted) versus continuous wave (mounted) laser threshold (typically less than 0.5 mA). These increases are much smaller than those specifically observed for other manufacturing processes. This is due to the good thermal contact between the metallization and the oxide formed according to the invention, as well as the good thermal state of the oxide. Furthermore, the surface layer which is heavily doped by the formation of the native oxide according to the invention is "used"
Is done. Thus, the doping of the high-jap shunt junction is low and the capacity is small. Compared to continuous wave operation, the leading edge of the pulsating current is significantly split between the electron well junction and the shunt IILD junction by the high shunt junction capacitance, which results in a significantly different pulsed versus continuous wave laser threshold. Low shunt capacitance diodes are more similar in pulsed and continuous wave laser thresholds than high capacitance ones.

FIG. 18 shows the field pattern of a 3 μm stripe laser for a continuous wave operating at 12 mA. FIG. 18 (a)
The near field pattern is about 3.4 μm in width and half of the maximum, and as shown in the SEM micrograph, about 3 μm
It is fairly close to an activation region with a width of m. In the far field of FIG. 18 (b), all angles are 20.4 ° and half of the maximum,
It corresponds to the diffraction limiting operation of a 3 μm stripe.

Example 6 Natural oxide stabilization of AlAs-GaAs heterostructure In this example, the high quality and high stability characteristics of the native oxide formed according to the present invention and the oxidation formed at a lower temperature than what is actually defined in the present invention It compares the low quality and fracture properties of objects. In particular, in this example, the quality of the native oxide exposed to water vapor at 400 ° C. for 3 hours at 400 ° C. and the conditions for the oxide formation are 375 ° C. and the oxide (S ).

The crystal used in this experiment was EMCOREGS at 760 ° C
Formed on a (100) n-type GaAs substrate by metal organic chemical vapor deposition (MOCVD) in a 3000 DFM reactor. The crystal growth pressure, group V / III ratio, and growth ratio are 100 Torr, 60, and about 1000 Å / min, respectively. Almost
A 0.5 μm thick undoped GaAs layer is formed first, followed by an approximately 0.1 μm thick apparently undoped AlAs layer. The crystal is split in two. Half of the cracked crystal has been exposed to room temperature atmospheric conditions (sample a). N ₂ carrier gas (flow rate of about the other half is held in 95 ° C. was H ₂ O Foam
Based on the method of the present invention at a temperature of 3 hours 400 ° C. in H ₂ O vapor environment obtained by passing the 1.5 scfh) is oxidized (sample b). Sample (b) has been exposed to the same atmospheric conditions as sample (a).

Within a few hours after exposure, the crystals of sample (a) begin to turn yellowish brown, while the crystals of sample (b) remain uniform blue (the oxide is clear and transparent, the blue is Optical effect). Figure 19 shows the surface of the crystal samples (a) and (b).
rski) Image photographs, in each case 100 days of exposure to air. The surface of sample (a) is clearly "rough" than the surface of sample (b). After 100 days of aging, sample (a) shows signs of non-uniformity around the edges of the crystal, while sample (b) remains unchanged. The oxidized surface of sample (b) is smoother than the surface of sample (a), and sample (b)
The cracked end of the sample is unchanged, while the end of sample (a) shows signs of destructive attack (as indicated by the roughening).

FIG. 20 is a scanning electron microscope (SEM) image for the edges of samples (a) and (b).
The edges are unfired, cracked sections and have been aged for 100 days. Sample (a) shows signs of chemical damage in the crystal, but this depth is well beyond the approximately 0.1 μm thick AlAs upper layer of the As-formed crystal. Conversely, the cross section of sample (b) shows a native oxide layer of substantially the same thickness as the AlAs upper layer of the As-formed crystal, the thickness of this native oxide being approximately 0.1 μm; Changes (deterioration) to natural oxides
There are few signs of Non-uniform etching also appears in the cross section of sample (a). It is surprising that the sample was not baked to emphasize this layer.

FIG. 21 shows the results of second ion mass spectrometer (SIMS) analysis of samples (a) and (b) taken after 80 days.
Is shown in In both samples (a) and (b), the oxygen and hydrogen signals on the upper side having a thickness of 0.1 μm are large (Al-
O-H ion number). What is unusual is that the sample (a) has an Al-O-H ion number of about 0.
It is shown that it is reduced at 1 μm. In sample (b), the Al-O-H signal is in sharp contrast, and the number of ions for Al-O-H decreases significantly after a thickness of approximately 0.1 μm, which is due to the natural oxidation. 2 shows a layer formed by an object. The number of Al-O ions follows the Al-OH signal in both samples. The other significant difference between the two crystals is the upper one in sample (a).
Ga depletion was apparent at μm, indicating that a chemical reaction and a change (deterioration) of the crystal had occurred. The Ga signal of sample (a) increases at the AlAs-GaAs interface, ie, about 0.1 μm, and decreases again at the surface; however, no “spike” in the Ga signal is observed for sample (b), Furthermore, this sample (b)
Shows no signs of chemical reaction or change (deterioration); these results are in accordance with the SEM image of FIG.
This shows that the native oxide formed from approximately 0.1 μm of sample (b) by the method of the present invention is characteristically stable.

SIMS analysis shows that the dip in the Al-OH signal is about 0.1 for sample (b), but this dip is absent for sample (a). Similarly, the transmission electron microscope image of the oxidized heterostructure is roughly 60% to 70% of the original thickness of the AlAs top layer.
% Indicates that there is some reduction in the native oxide layer. This reduction is one of the products of the Al-H ₂ O reaction, it does not adversely affect the quality of the oxide when there is an appropriate amount AlO (O
H) Explained by the fact that the molar volume is 25% less than the molar volume of AlAs (the molar volume of anhydrous α and the phase of Al ₂ O ₃ are approximately equal to that of AlAs, but this AlAs is It shows that α-Al ₂ O ₃ is formed as a main component). AlAs layer reduction from about 0.06 μm to 0.07 μm indicates that AlO (OH) is an intermediate or last oxide of the present invention (as indicated by the dip in the Al-OH signal). It is shown that. Further reductions in thickness are caused by arsenic losses. Reaction in the AlAs oxide is as _{follows: AlAs + 3H 2 O → Al} (OH) 3 + AsH 3 ↑ (1) AlAs + 2H 2 O → AlO (OH) + AsH 3 ↑ (2) 2AlAs + 3H 2 O → Al 2 O 3 + 2AsH 3 ↑ (3) The reaction of As ₂ O ₃ formation is the consumption of As in the AlAs layer in both the samples (a) and (b) (as shown in FIG. 21).
There is little if any increase.

Reaction (1) occurs in sample (a) and is related to the quality of the diode (s) formed; standard heating for the formation of Al (OH) ₃ is a-Al ₂ O at 300 ° K. ₃ , γ
-Al ₂ O ₃ or higher than the ALO (OH). This is 300 at atmospheric pressure
It corresponds to a phase diagram showing a thermodynamically stable phase of ゜ K. E. Related figures
M. Levin et al., "Phase Diagram for Thermistes" (Cermist Church, Columbus, Ohio),
See Fig. 2008, P. 551 (1964); Fig. 1927, P. 527 (1964) and Fig. 4984, P. 426 (1975).

As shown in FIG. 21, the first 0.1 μm of sample (b)
As a result, the consumption of As is two orders larger than that of the sample (b). As a result, the sample (b) Al
A second reaction is shown to occur in the As layer, which liberates more As (as volatile AsH ₃ ), thereby increasing the shrinkage of the native oxide layer. This reaction is as follows: AlO (OH) + AlAs + H ₂ O → Al ₂ O ₃ + AsH ₃ ↑ (4) Compared to sample (a), larger As was introduced into the AlAs layer of sample (b). The depletion indicates that As plays an important role in the formation of the stable native oxide of the present invention and furthermore catalyzes the reaction of the hydroxyl group (OH ⁻ ) in AlAs. The presence of the hydroxyl group makes the oxide of the sample (a) unstable, and it is considered that the oxide is insufficient from the conventional thermal oxidation technology.

As a gallium oxide compound, gallium trihydroxide Ga
(OH) ₃ is very similar to a Ga-OH compound formed at room temperature and atmospheric pressure. Gallium oxide hydroxide GaO (OH)
Takes the most stable form at about 400 ° C. Ga (OH) ₃ and GaO
(OH) is physically suitable for the intended use of the semiconductor, and further increases the thickness of the oxide. Ga (OH) ₃ and GaO (O
It is believed that H) is formed at a temperature of 375 ° C. as determined by the practice of this invention, and that undesirable amounts are formed by prior art thermal oxidation techniques. Ga (OH) ₃ is Al
Although the acid is stronger than (OH) ₃ , this Al (OH) ₃ acts as an acid or a base, and furthermore, the reaction of these two hydroxides has a detrimental effect that these materials have on the semiconductor structure. Strongly likely to worsen. Since both are electrolytes (when they are in the form of water), the reaction takes place in the presence of light.

The Ga-OH and Al-OH compounds are present in the native oxide of the present invention and are clear but do not damage the crystals of sample (b) as in sample (a). The reduction of special hydroxides at the high temperatures (above about 375 ° C.) used to form the native oxides of this invention stabilizes the reaction between Al—H ₂ O and Ga—H ₂ O. This suppresses the reaction of chemical damage due to low-temperature oxidation.

Example 7 and furnace forming rate 650 ° C. of native oxide by rapid thermal processing is applied to obtain a steam environment obtained through the N ₂ gas at 95 ° C. -105 ° C. of of H ₂ O bubbles; nitrogen gas flow rate of Is almost 1.4scfh.

To minimize the thermo-mass effect, the quartz board used to load the sample of this example is placed in a furnace until the sample is oxidized. The sample used is a crystal with an Al _x Ga _1-x As layer when _x is between about 0.8 and about 0.9.

The quartz board was removed from the furnace to oxidize the crystal, and the sample was placed on the board. Samples and boards are placed in this furnace. An oxidation period of about 15 seconds to about 10 minutes has been used for separate samples. The sample used at the end of the oxidation is quickly removed from the furnace.

For each sample, a native oxide formation rate is observed, resulting in a native oxide of about 0.1 μm (about 1000 °) that is formed using a rapid heat treatment according to the present invention at an oxidation time of every 15 seconds.

Example 8 Measurement of Refractive Index The native oxide layer is formed from four samples of Al _0.8 Ga _0.1 As (each layer is about 0.4 μm thick) overlaid on GaAs. Each of samples 1 to 4 contains Ga
There is an As cap (approximately 0.1 μm thick) which has been removed with a solution of H ₂ SO ₄ : H ₂ O ₂ : H ₂ O (1: 8: 80); Directly oxidized according to the procedure used. The oxidation times for samples 1 to 4 are 1, 2, 4, and 10 minutes, respectively.

Ellipsometer measurements using conventional equipment and a wavelength of λ = 6328 ° determine the thickness and refractive index of the oxide layer formed according to the present invention. The results are shown in Table 2 below: As is evident from Table 2, Samples 1 to 3 are almost completely oxidized, and the thickness of the resulting native oxide is approximately equal to or less than the thickness of Al _0.8 Ga _0.1 As. The refractive index of the native oxide thus formed is 1.54
The range of −1.57 indicates that the native oxide forming each sample is basically composed of a dehydrated aluminum compound.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Daresasse John M. 2684, Geneva Berkshire Drive 60134 Illinois, United States of America (56) References JP-A-2-91938 (JP, A) JP-A-56-71943 (JP, A JP-A-58-141524 (JP, A) JP-A-60-145283 (JP, A) JP-A-55-138238 (JP, A) JP-A-56-83946 (JP, A) 14094 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01S 5/00-5/50

Claims (99)

(57) [Claims] 1. A natural oxide containing aluminum-containing III-V
Wherein the native oxide comprises at least a portion of the aluminum-containing III-V semiconductor material to convert at least a portion of the aluminum-containing III-V semiconductor material.
Exposing the group-semiconductor material to a water-containing environment and a temperature of at least about 375 ° C., wherein the thickness of the native oxide is approximately equal to the thickness of the portion of the aluminum-containing III-V semiconductor. A method characterized by being less than or equal to. 2. The thickness of said native oxide is from about 0.6 to about 1.1 times the thickness of said aluminum-containing III-V semiconductor material.
2. The method of claim 1, wherein the time is between double. 3. The thickness of said native oxide is from about 0.7 to about 1.0 times the thickness of said aluminum-containing III-V semiconductor material.
3. The method of claim 2, wherein the factor is double. 4. The thickness of the native oxide is from about 0.8 to about 0.95 times the thickness of the aluminum-containing III-V semiconductor material.
4. The method of claim 3, wherein the factor is double. 5. The method of claim 1, wherein said native oxide has a thickness from about 0.85 to about 0.9 times the thickness of said aluminum-containing III-V semiconductor material.
5. The method of claim 4, wherein the factor is double. 6. The method of claim 1 wherein said water-containing environment comprises water vapor and an inert gas. 7. The method of claim 6, wherein said water-containing environment comprises nitrogen gas substantially saturated with water vapor. 8. The method of claim 7 wherein said nitrogen flow rate is at least about 0.5 standard cubic feet per hour. 9. The method according to claim 1, wherein said flow rate is about 2.0 per hour.
9. The method of claim 8, which is a standard cubic foot. 10. The method of claim 1, wherein said temperature is from about 375 ° C. to about 600 ° C. 11. The method of claim 10, wherein said temperature is from about 390 ° C. to about 500 ° C. 12. The method of claim 11, wherein said temperature is from about 400 ° C. to about 450 ° C. 13. The method of claim 10 wherein the time of exposing said aluminum-containing III-V semiconductor material to said water-containing environment and said temperature is from about 0.1 hours to about 6.0 hours. 14. The method of claim 13, wherein said time is from about 0.1 hours to about 5.0 hours. 15. The method of claim 14, wherein said time is from about 2.0 hours to about 4.0 hours. 16. The method of claim 15 wherein said time is about 3.0 hours.
The method described in. 17. The temperature range from about 600 ° C. to about 1100.
The method of claim 1, wherein the temperature is ° C. 18. The method of claim 17, wherein said temperature is from about 650 ° C. to about 1000 ° C. 19. The method of claim 18, wherein said temperature is from about 700 ° C. to about 900 ° C. 20. The method according to claim 19, wherein said temperature is about 800.degree. 21. The method of claim 17, wherein the time of exposing the aluminum-containing III-V semiconductor material to the water-containing environment and the temperature is up to about 120 seconds. 22. The method of claim 21, wherein said time is from about 5 seconds to about 90 seconds. 23. The method of claim 22, wherein said time is from about 10 seconds to about 60 seconds. 24. The method of claim 23, wherein said time is from about 15 seconds to about 30 seconds. 25. The method of claim 1, wherein the native oxide is free of hydrated aluminum compounds. 26. The method according to claim 1, wherein the native oxide is mainly composed of a dehydrated aluminum compound. 27. dehydrated aluminum compound of at least one of said method according to claim 26 which is α-A1 ₂ O _3. 28. The method of claim 26, wherein at least one of said dehydrated aluminum compounds is diaspore. 29. The method of claim 1 wherein said native oxide is free of aluminum suboxide. 30. The method according to claim 30, wherein the hydrated aluminum compound is A1 ₂ O ₃ .3.
The method of claim 25 comprising of H ₂ O and _{A1 2 O 3 · H 2 O} . 31. The aluminum suboxide according to claim 31, wherein η-A1 ₂ O
₃ , χ−A1 ₂ O ₃ , θ−A1 ₂ O ₃ , κ−A1 ₂ O ₃ , δ−A1 ₂ O ₃ , ι−A1 ₂ O
30. The method according to claim 29, having ₃ . 32. The aluminum-containing group III-V semiconductor material is AlGaAs, AlInP, AlGaAsP, AlGaAsSb, InAlGaP, In.
The method of claim 1 comprising AlGaAs. 33. The method of claim 1 wherein said native oxide is clean and substantially transparent. 34. The method of claim 1, wherein said aluminum-containing III-V semiconductor material is on a surface of an aluminum-free III-V semiconductor substrate. 35. The overlaid aluminum-containing material of claim 35.
35. The method of claim 34, wherein converting the III-V semiconductor material to the native oxide terminates at a surface of the aluminum-free III-V semiconductor substrate. 36. The method of claim 1, further comprising drying said native oxide in the absence of water. 37. The method according to claim 36, wherein said drying is performed in a dry inert gas. 38. The method according to claim 37, wherein said inert gas is dry nitrogen. 39. The method of claim 37, wherein said drying temperature ranges between about 375 ° C. to about 500 ° C. 40. The temperature range of about 400 ° C. to about 450 ° C.
40. The method of claim 39, wherein 41. The method according to claim 41, wherein the drying is the aluminum-containing.
37. The method of claim 36, wherein the method is performed after exposing the III-V semiconductor material to the water-containing environment at a temperature of at least about 375C for about 0.25 hours. 42. The drying time is about 2 hours.
41. The method according to 41. 43. The method of claim 1, further comprising annealing said native oxide. 44. The method of claim 43, wherein said native oxide is sealed in an ampoule. 45. The method of claim 44, wherein said ampoule comprises overpressurized arsenic. 46. The method of claim 45, wherein said ampoule has overpressured phosphorus. 47. The method of claim 43, wherein said annealing is performed in the absence of water, and wherein the temperature range is between about 600 ° C and about 850 ° C. 48. The method according to claim 47, wherein said temperature is about 850 ° C. 49. The method of claim 43, wherein said annealing time is from about 0.25 hours to about 4 hours. 50. The method of claim 39, wherein said drying temperature tends to increase within said range of about 375 ° C to about 500 ° C. 51. The method of claim 39, wherein said drying temperature has a downward trend within said range of about 375 ° C. to about 500 ° C. 52. The method of claim 43, wherein said annealing temperature has a tendency to increase in a range from about 600 ° C. to about 850 ° C. 53. The method of claim 43, wherein said annealing temperature has a downward trend within a range of about 600 ° C. to about 850 ° C. 54. The method of claim 1, wherein said temperature tends to increase from at least about 375 ° C. while exposing said aluminum-containing III-V semiconductor material to said water-containing environment. . 55. The method of claim 54, wherein said temperature tends to increase from at least 375 ° C. and said exposure time is from about 2 hours to about 4 hours. 56. The method of claim 54, wherein said temperature tends to increase from about 600 ° C. to about 1100 ° C. and said exposure time is from about 15 seconds to about 30 seconds. 57. The method of claim 17, comprising heating the aluminum-containing III-V semiconductor material for a heating time of about 2 hours or less. 58. The method of claim 57, wherein said heating time is less than about 1 second. 59. The method of claim 57, wherein said heating starts at about room temperature. 60. The method of claim 17, wherein said native oxide is formed at a rate of about 0.1 μm for each of said about 15 second exposure times. 61. When the natural oxide is x of about 0.7 or more, A1 _x Ga
In a way to form a _1-x As, the natural oxide of has A1 _x Ga _1-x As thickness less than or equal to that of the corresponding portion of the semiconductor material at least a portion of said of said semiconductor material Nitrogen and steam environment and about 400 ° C to about 4 to convert to natural oxide
A method comprising exposing to a temperature between 50 ° C. 62. The method of claim 61, wherein said nitrogen is substantially saturated with said water vapor and said flow rate is about 1.0 to about 3.0 standard cubic feet per hour. 63. The method of claim 61, wherein said exposure time is about 3.0 hours. 64. The method according to claim 61, wherein said native oxide is mainly a dehydrated aluminum compound. 65. A method wherein A1 _x Ga is used when x is about 0.7 or more.
In a way to form a _1-x As, the natural oxide of has A1 _x Ga _1-x As thickness less than or equal to that of the corresponding portion of the semiconductor material at least a portion of said of said semiconductor material Nitrogen and steam environment and about 600 ° C to about 1 to convert to natural oxide
A method comprising exposing to a temperature in the range of 100 ° C. 66. The method of claim 65, wherein said nitrogen is substantially saturated with water vapor and said flow rate is from about 1.0 to about 3.0 standard cubic feet per hour. 67. The method of claim 65, wherein said time is from about 15 seconds to about 30 seconds. 68. The method according to claim 65, wherein said native oxide comprises predominantly a dehydrated aluminum compound. 69. A semiconductor device comprising a native oxide formed from an aluminum-containing III-V semiconductor material, wherein said native oxide is said aluminum-containing III-V semiconductor material.
A water-containing environment to convert at least a portion of the III-V semiconductor material to the native oxide, at least about
Wherein the thickness of said native oxide is about equal to or less than the thickness of said portion of said aluminum-containing III-V semiconductor material. 70. The semiconductor device according to claim 69, wherein said device is an activation device. 71. The semiconductor device according to claim 70, wherein said device is an optoelectronic device. 72. The semiconductor device according to claim 71, wherein said optoelectronic device is a laser. 73. The semiconductor device according to claim 70, wherein said device is a capacitor. 74. The semiconductor device according to claim 70, wherein said device is a transistor. 75. The device according to claim 75, wherein the device is a waveguide.
74. The semiconductor device according to 71. 76. The semiconductor device according to claim 70, wherein said laser comprises a ridge waveguide. 77. The semiconductor device according to claim 70, wherein said laser has a single stripe configuration. 78. The semiconductor device according to claim 72, wherein said laser has a multiple stripe configuration. 79. The semiconductor device according to claim 72, wherein said laser is configured as a surface emitter. 80. The temperature range of about 600 ° C. to about 1100.
71. The semiconductor device according to claim 70, wherein the temperature is ° C. 81. The semiconductor device of claim 80, wherein said exposure time is between about 15 seconds and about 30 seconds. 82. The semiconductor device according to claim 80, wherein said device is a transistor. 83. The semiconductor device according to claim 71, wherein said optoelectronic device has a first quantum well in a second quantum well. 84. The semiconductor device according to claim 83, wherein said first quantum well comprises InGaAs and said second quantum well comprises GaAs. 85. A semiconductor device comprising: a layer of a semiconductor substrate; a first confinement layer on the layer of the substrate; an activation region on the first confinement layer; The second confinement layer above; the second confinement layer is the first aluminum-containing
Further comprising a current blocking layer overlying the second confinement layer; the current blocking layer being a surface of the second confinement layer to convert the second confinement layer to native oxide. Comprises a native oxide formed by exposing at least a portion of the native oxide to a water-containing environment at a temperature of at least about 375 ° C. for a sufficiently long time, wherein the native oxide has a thickness of the second confinement. A semiconductor device characterized by having a thickness approximately equal to or less than the thickness of a corresponding part of the layer. 86. The method according to claim 86, wherein said substrate layer comprises an aluminum-free III-V semiconductor material; said first confinement layer comprises a second aluminum-containing III-V semiconductor material; Is the third aluminum
At least two waveguide layers of contained III-V semiconductor material, and a quantum well heterostructure located between the waveguide layers, wherein the quantum well heterostructure is a fourth aluminum layer. 86. The semiconductor laser according to claim 85, comprising a group III-V semiconductor material. 87. The method of claim 85, further comprising a contact layer intermittently disposed on a surface of said second confinement layer in a region of said second confinement layer that cannot be converted to said native oxide. Semiconductor laser. 88. The semiconductor laser according to claim 87, wherein said contact layer is intermittently arranged in a single stripe configuration. 89. The semiconductor laser according to claim 87, wherein said contact layer is intermittently arranged in a multiple stripe configuration. 90. The aluminum-containing semiconductor for converting an aluminum-containing III-V semiconductor material to a native oxide.
A native oxide formed by exposing the III-V semiconductor material to a temperature of at least 375 ° C. containing water, wherein the native oxide has a thickness of the aluminum-containing II
Approximately equal to the thickness of the relevant portion of the IV semiconductor material,
Diffusion mask for semiconductor material, characterized by being smaller. 91. A diffusion mask according to claim 90, wherein said mask effectively diffuses zinc or silicon. 92. The natural oxide is aluminum-containing III-
Exposing said aluminum-containing III-V semiconductor material to a temperature of at least 375 ° C. in a water-containing environment to convert said Group V semiconductor material to said native oxide, The aluminum-containing III- in which the thickness of the oxide is changed to the native oxide
A native oxide composed of an aluminum-containing III-V semiconductor material, wherein the native oxide is approximately equal to or less than the thickness of the corresponding portion of the group V material. 93. The natural oxide according to claim 92, wherein said natural oxide mainly comprises a dehydrated aluminum compound. 94. The natural oxide according to claim 93, wherein said natural oxide does not contain a dehydrated aluminum compound. 95. The natural oxide according to claim 93, wherein said natural oxide aluminum compound has α-A1 ₂ O ₃ and diaspore. 96. The temperature range is from about 600 ° C. to about 1100
94. The native oxide of claim 93 which is at ° C. 97. The native oxide of claim 96, wherein said exposure time is from about 15 seconds to about 30 seconds. 98. The natural oxide has a refractive index of λ = 6328 °.
93. The method of claim 92, wherein said is less than about 2.0. 99. The native oxide of claim 98, wherein said refractive index is between about 1.54 and about 1.57.