JPS61214527A - Low resistance n- type semiconductor thin film and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the reproducibility and the mass-productivity by a method wherein, when an N<-> type semiconductor layer to be an active layer or a closed layer of light emitting diode, laser diode etc. is formed, III group elements as donor impurity are contained in single crystal zinc sulfide thin film. CONSTITUTION:When an N<-> type semiconductor thin film is grown on a substrate made of GaAs, GaP and Si etc., the substrate is heated in a heating furnace fed with carrier gas containing material gas to be epitaxially grown. At this time, as for donor impurity, either one of Al, Ga, In or mixture of these elements is contained in single crystal zinc sulfide; or as for zinc source, dialkyl zinc and dialkyl sulfur or an additive produced from equimole mixture of dialkyl selenium are used; and as for sulfur source, hydrogen sulfide is used. Through these procedures, the dependability upon growing temperature may be made excellent enabling to emit dark blue light at room temperature when excited.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a low resistance ZnS single crystal thin film used for the active layer or confinement layer of a light emitting diode (LED) or laser diode (KID), and a method for manufacturing the same.

<Summary of the Invention> The present invention is characterized in that a low resistance n-type semiconductor thin film used for the active layer and confinement layer of LICD and LD includes a group I element as a donor impurity in a zinc sulfide single crystal thin film. This makes it possible to create light-emitting devices using zinc sulfide.

Furthermore, in the manufacturing method, a zinc sulfide thin film &
By simultaneously supplying an organometallic compound of a feared element, a low-resistance n-type ZnS single crystal thin film can be produced while controlling donor impurities. It is.

<Prior Art> Zinc sulfide (ZrLS), which is a direct transition type wide-gap compound semiconductor, has a band gap of about λ6 eV at room temperature, and is attracting attention as a material for short wavelength light emitting devices. Until now, high-grade Zn has been produced using various crystal growth methods.
Attempts have been made to produce a S single crystal thin film, but a single crystal thin film that can be used for device fabrication has not yet been obtained ◇ This is because the constituent elements Zn and 9 both have high vapor pressures, making crystal growth difficult. This is because lattice defects are easily included in the process. In order to suppress lattice defects, K is said to be one method to lower the growth temperature75, and in recent years, the organic gold j11 vapor phase pyrolysis method (MOO'VD method), which allows crystal growth of ZnS at low temperatures, has been developed. ), molecular beam epitaxy (MI
E method) etc. are attracting attention.

MOOVD and MBIC methods allow crystal growth at lower temperatures than liquid phase epitaxial growth and chemical vapor deposition (OVD) methods, and they also allow crystal growth to occur in conditions where the crystal growth process deviates significantly from the thermodynamic equilibrium state ( Since the process proceeds in a non-equilibrium state (1 m1), it is possible to suppress the generation of lattice defects and the incorporation of impurities.

High quality single crystal thin films have been reported by MOOVD and MBE methods. (For example: Tapanese J, Appl, Phys, 2
2 (19B3) ll583J, 0rys+ta engineering G
rowth, jj- (1981) 423) Z
nS f:Xr MD In order to apply to LD and LD,
It is necessary to control the conductivity type and resistivity by doping with impurities. As mentioned above, ZnB easily contains lattice defects.
It is extremely difficult to control the conductivity type and reduce the resistance of the thin film, and in particular, there is no prospect of producing P-type ZnB even by using the MOaVD method or the MBK method.

Since Zn19 is n-type in nature, it is thought that it is relatively easy to produce an n-type ZnS single crystal thin film, and several experimental examples have been reported. An outline is given below.

1. ZnS grown on Q&Aa by the low-pressure MOOVD method using dilfk zinc (DMZ) and hydrogen sulfide (H, 8) is in an undoped state without the addition of impurities, and in an as-grow state. showed low resistivity. For example, at a growth temperature of 300° C., the specific resistance ρ was 1Ωs1.

(45th Japan Society of Applied Physics Academic Conference 1984 Autumn Conference Proceedings 12a-3-5630) ZnS grown on GaAs by the MBE trap using 2211LS as a source is in an undoped, am-gro state. , ρ+toHatakeΩ・1. The growth temperature at which ρ was minimized was around 240°C.

(, T, 0rystal Growth it ((
1984) 125. ) Triethylaluminum (TI
The ZnS resistance introduced with CAI) and added with A1 also changed, and exhibited a minimum value at 400°C. But 400
Even at ℃, the value of ρ was as large as 104Ω·1, which was not at a level that could be applied to devices.

(Hxtended ab*traats or th
e xsthOonferanae on 5olid
St&te D・Maassan4 Materia
ls, Tokyo, 1983. pp, 349
-352) <Problem and purpose to be solved by the invention>
Since ZnS has a bandgap of λ6sV at room temperature, high-grade ZnS should exhibit high resistance. Therefore, the undoped low resistance ZnS shown in Prior Art 1.2
It is thought that the resistance is low due to the low crystal quality. In other words, there is a strong possibility that the included lattice defects or the impurities taken in during the growth process are sources of free electrons. Therefore, it is difficult to apply to device fabrication because the reproducibility of the resistivity is poor and the resistivity cannot be changed intentionally.

In prior art 3, impurity doping was performed for the purpose of intentionally changing the resistivity, but the resulting Zn
S has a high resistance of ρ: 104Ω, so it cannot be applied to devices.

An object of the present invention is to create a ZnS single crystal thin film with a low resistance technically controlled by doping with an impurity element, which has not been achieved so far.

<Means for Solving the Problems> The present invention is characterized in that a zinc sulfide single crystal thin film contains a group I element as a donor impurity. Furthermore, in the manufacturing method, when a ZnS single crystal thin film is formed by the M00VD method using an adduct obtained by equimolar mixing of dialkyl zinc and dialkyl sulfur or dialkyl selenium as a zinc source and using hydrogen sulfide as a sulfur source, l The method is characterized in that a low resistance n-type ZrxF3 single crystal thin film is produced by simultaneously supplying an organometallic compound of group elements. The adduct here includes not only a coordination compound obtained by acid-base and core when dialkyl zinc and dialkyl sulfur (dialkyl selenium) are mixed in equimolar amounts, but also a mixture obtained by equimolar mixing. Furthermore, in the mixture, the case where three chemical species coexist is also included, with some forming a coordination compound and the others dissociating into dialkylzinc and dialkylsulfur (dialkylselenium).

FIG. 1 is a schematic diagram of a MOOVD apparatus used in producing a low resistance n-type ZnS single crystal thin film in the present invention.

Si is inside the horizontal reaction tube made of quartz glass.

A coated graphite susceptor (■) is placed, and a substrate (■) is placed on top of it. High frequency heating furnace, infrared furnace from the side of the reactor.

Alternatively, heat the substrate using a resistance heating furnace (2) or the like.

The substrate temperature is monitored by a thermocouple embedded in a graphite susceptor. The reaction tube is connected to the exhaust system (2) and the waste gas treatment system (2) via the pulps (2) and (2). An adduct obtained by equimolar mixing of dialkylzinc, which is a Zn source, and dialkyl sulfur or dialkylselenium is enclosed in a bubbler (2). Also, an organometallic compound 2 that serves as a source of group I elements, such as triethylaluminum (TEAL), )rimethergallium (TMGa).

Bubbler such as triethyl indium (TIc-n)
is enclosed in.

The carrier gas and hydrogen sulfide are each filled in a cylinder at 0°■. The carrier gas and hydrogen sulfide purified by the purifier are each controlled in flow rate by a mass flow controller. The adduct and the Otori group organometallic compound encapsulated in the bubbler [phase] and (2) are each maintained at a predetermined temperature by a constant temperature bath [phase].

By introducing an appropriate amount of carrier gas into this bubbler and performing bubbling, a desired amount of adduct and liter can be obtained.
Group organometallic compound is vaporized and supplied. bubbler [phase]
, (2) and the adduct two-layer group organometallic compound and hydrogen sulfide supplied from the cylinder 0 are each diluted with a carrier gas and combined, and then introduced into the reaction tube (2) through the three-way pulp 0. The three-way pulp (2) switches the introduction of the raw material gas into the reaction tube and the disposal to the waste gas treatment system (2). Figure 1 shows that the basic structure of the outer layer is the same as that of the M-type anti-broad furnace. However, it is necessary to ensure the uniformity of the obtained film by providing a rotation mechanism for the substrate.

A specific manufacturing process for a low resistance n-type ZnS single crystal thin film containing group I elements will be explained below.

Gallium arsenide (Q&A!I), gallium monophosphide (GaP), which is sliced in a plane with a deviation of 5° or 2@ from the (100) plane, (1oo) plane to the (lzo) plane, and polished to a mirror finish. Silicon (Sl) is etched after being subjected to ultrasonic cleaning using trichloroethylene, acetone, and methanol.

The etching conditions are as follows.

GaAa substrate H, So, :H, O, :H, Q==3
: 1 : 1c volume ratio) 2w1n GaP substrate at room temperature HOl:HNO,==31 (volume ratio) 30 aaaS1 substrate HF:H,0==1:1(
Volume ratio) 2 at room temperature! Etching was stopped using 11 inches of pure water, washed with pure water and methanol, and then stored in a Daiflon.

Immediately before setting the substrate in the reaction tube, the substrate is taken out from the Guyflon, and the Daiflon is dried and removed by dry nitrogen blowing. After setting the base, vacuum the inside of the reactor to about 1" Torr to remove residual gas in the system. After introducing carrier gas and returning the inside of the system to normal pressure,
Start heating up while flowing a carrier gas of about 100 mL. An infrared heating furnace was used for heating. As the carrier gas, He with a purity of 99.9999% or R2 passed through a purification device was used. After the substrate temperature reaches the predetermined temperature and becomes stable, the supply of raw material gas is started and the low resistance is 2nS.
Conduct membrane growth. However, in the case of an 81 substrate, it is necessary to clean the substrate surface by heat treatment at 900° C. for about 10 minutes in a hydrogen stream. The purity of the adduct used was 99.9.
It is an adduct obtained by mixing equimolar amounts of 999% dimethylzinc and diethyl sulfur. This adduct has a vapor pressure of about 2801111 Hg at 3 o'c. Triethylaluminum (
rx*1) was used.

The growth conditions are as follows.

, substrate temperature 350''c, distance from RL material inlet to substrate 20cm, adduct bubbling amount at -15°C 30 r+l/min, TEA 1 bubbling amount at -10°C 20 ml/win,
Supply amount of 2% H,3 diluted with He 200 ml/
win, total gas flow rate including carrier gas 4.
5 l/mtn, growth time 90 win After performing growth for a predetermined time, the supply of raw materials is stopped and cooled. During cooling, He or R1 is 1-21/m
Let it flow in. He was used to prevent thermal etching of the substrate surface.
Cooling may be performed while flowing diluted 2% H, S at about 50 to 60 m4/+1n. When the substrate returns to room temperature, the reactor is evacuated to remove hydrogen sulfide remaining in the system. After returning the system to atmospheric pressure, remove the substrate. The thickness of the Zn5jAl film obtained at this time was about 1 μm, and the growth rate was about 0.7 μm/hr.

The Zn8:Al single crystal thin film produced by the above process has a specific resistance of about 0.1 to Zo at room temperature.

It showed values on the order of Q with good reproducibility. Growth temperature 300℃
When the temperature was varied between
The minimum value was observed at around 70°C. The growth temperature dependence of resistivity also had good reproducibility.

At a growth temperature of 350°C, Tl! When changing the bubbling amount of iAl at 10℃, 15mJ/win
A decrease in resistivity was observed as the amount of bubbling increased in the range from 15 m to 25 ml/win, but
If less than l/win or 25 ml
/min, a rapid increase in resistivity occurred.

When the obtained low-resistance ZnS film was excited with a He-Od laser (oscillation wavelength 32 s OA'), it exhibited strong blue light emission (emission wavelength 460-470·fl) at room temperature.

An example of the photoluminescence spectrum of a low resistance Zn3 film at room temperature is shown in FIG.

Even when the excitation wavelength was changed from 250 m to 40 Qsni using a xenon lamp, no emission other than light emission around 460 to 470 m was observed. The above facts indicate that the ZnSjAm thin film produced by the present invention is of extremely high quality.

TmA 1G Doinyu 1.8L/-1〒Kousa Roku! Now zn S
II t[〒 showed a high resistivity of at least 10'Ω·1 or more, and no 7 otoluminescence near 470x was observed. It can be seen that the decrease in resistivity and the 7 ounces are due to the doping of A1.

In the above explanation, we have described some adducts that can be obtained by equimolar mixing of dimethylzinc and diethyl sulfur.
In addition, dimethylzinc and dimethylsulfur (vapor pressure at 20°C: about 120mIg).

Diethyl zinc and dimethyl sulfur (vapor pressure approximately 88 Hg at 30'C) and diethyl zinc and diethyl sulfur (vapor pressure approximately 88 Hg at 30'C)
Combination adducts, such as those obtained by equimolar mixing of dialkyl zinc and dialkyl sulfur (with a vapor pressure of about 151,111 Hg at °C), can also be used in the same manner as the adducts of dimethylzinc and diethyl sulfur, and are within the scope of the present invention. It is. In addition, four types of adducts obtained by combining dimethylselenium, diethylselenium, dimethylzinc, and diethylzinc, which do not decompose at growth temperatures of 400°C or lower, can also be used in the same way as alkylselenium adducts. However, it is included in the present invention.

As can be easily inferred from the above explanation, A1 to znS
Similarly to the addition of Ga, In, the corresponding organometallic compound, such as triethylgallium (boiling point = 14
3°C) and triethyl indium (boiling point = 184°C). When the supply amount calculated from the vapor pressure at the bubbling temperature and the bubbling gas flow rate is equal to that of triethylaluminum, the obtained Z
nS:Ga, ZnS:N exhibited electrical characteristics similar to ZnS:Al. According to the present invention, the production of low-resistivity ZnS single crystal thin films controlled by doping is possible by adding Zn
This was made possible by the MOOVD method used as a source.

The production of a blue light emitting element will be described below as an example of device application of the low resistance ZnS produced according to the present invention.

1. On an n-type GaAa substrate sliced along the (Zoo) plane, an A1-doped low-resistance Zn8 layer is grown to a thickness of about 3/Jl according to the MOOVD process described above. .

2 A u-G o (G o = 12
vrt-%) to about 200 OA', heat treatment is performed at 350° C. for 5 to 10 minutes in an inert atmosphere to form an ohmic contact to the GaAs substrate.

λ Sputtering approximately 100 OA' of Sin and Zn
Stack it on S.

4, S10. Thickness 300-500A on top! Au translucent electrodes of about 100 mL are laminated.

When a forward bias voltage is applied between the surface Au electrode of the device having the M/S structure fabricated as described above and the 9 ohm contact provided on the Q&A11 substrate, light emission is observed from around 1 to 2 V. It was done. The emission spectrum had a peak around 460 to 4701111 at room temperature, and the emission intensity increased in proportion to the current flowing through the device. The quantum efficiency was approximately 10-1.

M having a light emitting layer of Zn8:Al formed according to the present invention
Due to the confirmation of blue light emission in the 8-type device,
It was demonstrated that the low resistance znS manufactured by the present invention has a quality suitable for device fabrication.

The low resistance n-type semiconductor thin film based on the present invention can be applied to the above-mentioned MIS.
It is easy to apply not only to type blue light emitting devices, but also to homojunction devices formed by stacking with p-type Zn8, as well as LEDs, LDs, etc. that utilize petrojunctions formed between other compound semiconductors. It is.

<Effects of the Invention> As described above, according to the present invention, an adduct obtained by equimolar mixing of dialkyl zinc and dialkyl sulfur or dialkyl selenium is used as a zinc source and H and S are used as sulfur sources in the MOOVD method. When forming a JZnS single crystal thin film, by simultaneously supplying an organometallic compound of group I elements, a low resistance n-
The fabrication of a type ZnS single crystal thin film was realized. Furthermore, it has become possible to manufacture the thin film while controlling donor impurities. We are confident that the present invention, which uses the MOOVD method with excellent reproducibility and mass production, will greatly contribute to the production of active layers and containment layers for LEDs and LDs, which are mainly in the blue region, which are extremely important for display purposes. do.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the M00VD apparatus used in the present invention 1 Reaction tube made of quartz glass 2 Susceptor made of graphite coated with SiO 3 Substrate 4 High frequency heating furnace, infrared furnace, or resistance heating furnace 5 Thermocouple 6 Exhaust system 7 Waste gas Processing system 8.9 Pulp 10 Bubbler containing adduct 11 Bubbler containing organometallic compound of group element 12 Cylinder containing carrier gas 13 Cylinder containing hydrogen sulfide 14 Gas purification device 15 Mass flow controller 16 FFL temperature Tank 17 Three-way pulp
18 Pulp Figure 2 shows the 7 otoluminescence spectrum of low-resistivity ZnS:A1 produced according to the present invention.

Claims (4)

[Claims] (1) As a donor impurity in zinc sulfide single crystal thin film
A low resistance n-type semiconductor thin film characterized by containing a group III element. (2) In claim 1, a low resistance n characterized in that the Group III element contained as a donor impurity is one or more of Al, Ga, and In.
- type semiconductor thin film. (3) Forming a zinc sulfide thin film by metal organic vapor phase pyrolysis (MOCVD) using hydrogen sulfide as the sulfur source and using an adduct obtained by equimolar mixture of dialkylzinc and dialkylsulfur or dialkylselenium as the zinc source. A method for producing a low-resistance n-type semiconductor thin film, which comprises simultaneously supplying an organometallic compound of a group III element. (4) In claim 3, the organometallic compound simultaneously supplied when forming the zinc sulfide thin film is Al, Ga, etc.
A method for producing a low-resistance n-type semiconductor thin film, characterized in that it is made of one or more of organometallic compounds of , In.