JPS62274790A - Optical and electronic integrated circuit and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase the light confining effect, and to reduce the threshold current of a photo electron integrating circuit by a method wherein quantum well structure is adopted as the active layer of an LU to enlarge oscillation level density, gain is enhanced to contrive to reduce an oscillation threshold current, and both the sides of the active layer are made to have gradient band gap structure. CONSTITUTION:A second semiconductor layer 4 having gradient band gap structure is consisting of an n-type AlGaAs layer, the rate of composition of Al is (x) at the boundary between a semiconductor layer 3, the rate of composition of Al is zero at the boundary between a semiconductor layer 5, and the rate of composition of Al varies continuously corresponding to thickness of the layer at the midway between them. A third semiconductor layer 5 of narrow gap is consisting of a quantum well layer (impurity concentration is 5X10<17>/cm<3>) of n-type GaAs or undoped GaAs, thickness thereof is the degree of 50-300Angstrom , and to be used as the active layer of a laser diode (LD). A fourth semiconductor layer 6 having gradient band gap structure is consisting of p-type AlGaAs, the rate of composition of Al is zero at the boundary between the semiconductor layer 5, the rate of composition of Al is (x) at the boundary between a fifth semiconductor layer 7, and the rate of composition of Al varies continuously corresponding to thickness of the layer at the midway between them. The fifth semiconductor layer 7 of wide gap is consisting of p-type AlGaAs, and the layer thereof is the part to be used as the clad layer of the LD.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a semiconductor light source device capable of high-speed modulation and used as a communication transmitter.

(The problem to be solved by the prior art and the invention is that the optoelectronic integrated circuit (optOelectri
c Integrated C1rcuit Below,
0EIC) is effective in making optical transmitters more confusing and more reliable. In particular, heterostructure bipolar transistors (Heterostructure Bipo
lor Transister (hereinafter referred to as HBT and ligand)
0EIC has high current drive capability and high speed operation.
It is suitable as an electronic device.

This ZHBT and laser diode (La5erDi)
ode (hereinafter referred to as LD) is an example of a combination of log IC, as reported by J. Katz et al. (Ap
pl, Phys, Lett, 37(2), 198
0). Figure 3 is shown in the above report tL7'C4#
This device is based on an n''-GaAs substrate 20.
On the top, the substrate side area No. 11 W n -AlGaAs 21
, 284th p-GaAs 22, 3rd NIn-
AlGaAs 23 epitaxial film grown and npn
By manufacturing an HBT with structural engineering 9 and press-fitting Be ions up to the third layer of okara p-GaAs 22,
A part of the n-AtcaAs of 37123 was replaced with the tp type 24, and a device was devised so that it could be operated even with an LD having an npp structure. However, this structure has some disadvantages.

(a) Since the base layer of HBT is also used as the active layer of LD at the same time, it is necessary to prevent light absorption by free carriers, and the carrier concentration of this layer is high (≧5XIOI? α-39 cannot be achieved.On the other hand, HBT As for the operating speed, as can be seen from the standard cut Co: given by collector chamber arm, the operating speed becomes faster as the base resistance decreases.

Therefore, with the structure of Kaatsu et al., in which the base resistance cannot be sufficiently reduced, it is difficult to create a device capable of high-speed operation.

(b) Since an n+ substrate is used and the bottom surface of the substrate is used as the collector electrode, the collector area is large.
is large. Therefore, as can be seen from the fc table hole mentioned earlier, it is not suitable for increasing the speed of HBT.

(9) The collector electrode is on the bottom surface, making it difficult to separate elements and conduct wiring.

As explained above, it can be said that Kaatsu et al.'s device poses problems in terms of speeding up and integration.

(Tth Means for Solving All Problems) The object of the present invention is to solve the above-mentioned problems, namely, B) HBT.
, the structure is not suitable for improving the performance of each LD (b) The object is to solve the problem that integration is difficult in terms of isolation between elements, wiring, etc., and to provide a 90EIC that is high-speed and suitable for integration.

To achieve the above object, the present invention provides a wide gap first semiconductor layer of a first conductivity type, #4, on a semi-insulating substrate.
a second semiconductor layer of a first conductivity type having an oblique band gap; a third semiconductor layer of a first conductivity type or a narrow gap with no impurity added; 'W having an oblique band gap;
A fourth semiconductor layer of J24 type and a fifth wide-gap semi-quadruple layer of a second conductivity type are sequentially stacked in a first region in a constant multilayer epitaxy cell film, and a third semiconductor layer is formed as an active layer. , the first and fifth semiconductor layers are all cladding layers GRIN-S
A CH laser is constructed and the second laser in the multilayer epitaxial film is
In the region, the first to third semiconductor + m t collector,
4th. A heterojunction bipolar transistor is constructed in which the 14th turtle-shaped impurity region formed in the fifth semiconductor layer is the emitter, and the entire region is the base, i''L7t sandwiched between the emitter and collector in the fourth semiconductor layer. The gist of the invention is an optical/electronic integrated circuit characterized by the following.

Further, in the present invention, a wide-gap first semiconductor layer of a first conductivity type, a second semiconductor layer of a first conductivity type having a sloped bandgap, a 14th conductivity type semiconductor layer, or an impurity layer are formed on a semi-insulating substrate. forming a multilayer epitaxial film by sequentially stacking a narrow-gap third semiconductor layer without additives, a fourth conductivity type semiconductor layer with a graded bandgap, and a wide-gap fifth conductivity type semiconductor layer; L on the insulating layer, first
GRIN-S is separated into a region and a second region, and in the first region in the multilayer epitaxial film, the third semiconductor layer is an active layer, and the first and fifth semiconductor layers are cladding layers.
A CH laser system is configured, and in a second region within the multilayer epitaxial film, a fourth. A first conductivity type impurity region is selectively formed in the fifth semiconductor layer using an ion implantation method, and the first to 8g3 semiconductor layers are used as a collector, and the fourth and fourth semiconductor layers are used as a collector. Formed within the fifth semiconductor layer 7? , an optical/electronic integrated circuit comprising a 14'tJL type impurity region as an emitter, a 9 region sandwiched between an emitter and a collector in a fourth semiconductor layer, and a heterojunction bipolar transistor as a base. The gist of the invention is the way of reading +9-.0 The features of the present invention are as follows.

(a) As the active layer of the LD, an electron well structure (impurity concentration 5 x lQ"/crn') is adopted to increase the density of excavated levels and increase the gain, thereby reducing the oscillation threshold current. By forming both swm diagonal bandgap structures, the light confinement effect can be increased and the threshold value vL flow can be further reduced.

(b) In the conventional structure in which the active layer of the above LD is shared with the base I- of the HBT, it is an active Nt footwell structure, so when the layer is thinned (~0.01 μm), the base resistance increases, and the HBT Friend has the disadvantage of slow operation speed.

In this regard, in the present invention, by using only one of the two graded bandgap layers as the base layer of the 7HBT, it is possible to avoid making the base layer thinner (up to 0.2 μm).

B1 In addition, by using one of the graded bandgap layers as the base layer of the HBT (appropriate impurity carbon content of approximately 5XlO'cm'), an electric field is generated in the base layer and carriers are accelerated. It has a structure.

Due to this acceleration, the carriers have a higher diffusion speed (drift speed V) than the conventional uniform base, and as a result, the current amplification factor can be increased.

(f) A film with a pn structure, which is the basis of the LD, is formed as an epitaxial film, and an n-type impurity region reaching 1 is formed in the upper inclined bandgap layer by ion implantation or vapor phase diffusion to form an emitter. Fabricate HBTk with npn structure. LD and HBT can be mounted on the same substrate with this simple process.

(e) Since a semi-insulating substrate is used, elements can be isolated.

Wiring can be done easily and at the same time, collector capacitance can be reduced, so high-speed operation of the device is possible.

(f) LD active layer (appropriate impurity concentration ≦5 x 10
'7z HBT base layer (appropriate impurity concentration approximately 5x
By setting appropriate impurity concentrations for 10I and cPn, respectively, the threshold current of the LD can be lowered and the HBT can be reduced.

The cutoff frequency can be increased.

As explained above, the FC element structure is compared with the conventional one.

The overall layer structure, especially the structure of the active layer, is completely different.

Next is the implementation of non-invention? lj kThe attached drawings will be explained.

It should be noted that the embodiments are merely illustrative, and it goes without saying that individual changes and modifications may be made without departing from the spirit of non-invention.

FIG. 1 shows an embodiment of the invention, showing the vertical structure of the device. In the figure, 1 is a semi-insulating GaAs substrate, 2
rLLD and HBT = n+- to take the z rector cage pole
GaAs layer 3 is a wide gap first semiconductor layer with n
-At, Ga1, As (0(x<]) processing n5,
LD cladding and HBT collector layer, 4 is a second semiconductor layer with a 1#4 oblique band structure, and is made of n-AlGaAs.
At the layer edge, the M composition ratio is 2 at the boundary with the semiconductor layer 3.
, the M composition is zero at the boundary with the semiconductor layer 5, and in between,
The M composition changes continuously with the layer thickness.

5 is a third semiconductor layer with a narrow gap, and is made of n-GaAs.
Or undoped GaAs (1) Quantum well layer (impurity concentration 5XlO'nm'), the thickness of which is 50~3(1
0) At about A, it becomes the active layer of the LD. Is 6 a sloped band structure? The fourth semiconductor layer has a p-AAs process9,
The M composition is zero at the boundary with the semiconductor layer 5, the μM composition is 2 at the boundary with the semiconductor layer 7, and the M composition changes continuously over the 7 m thickness. 7 is the wide-giang fifth semiconductor layer, which is made of p-AlGaAs and becomes the cladding 11# of the LD, and 8 is the p''-
When GaAa is used, the HBT's base 4 poles and the LD's p pole are all taken.

9 is 7tn formed by ion injection or vapor phase diffusion method.
The depth of the type impurity region is made to reach a part of the graded bandgap layer of the semiconductor layer 6. It becomes the emitter of HBT.

HBT base and emitter at B, E, and C, respectively.

Collector electrodes P and N indicate electrodes of the LD, respectively.

Next, the manufacturing method will be explained.

A semiconductor layer 2 of n-Ga is formed on a semi-insulating substrate 1 of GaAs.
As1 is formed, then a wide-gap first semiconductor layer 3 of n-AlGaAs is formed, and then a second semiconductor layer with a sloped bandgap is formed of rl-AlGaAs of /m4.
Forms As. In this case, the composition ratio of M is X at the boundary with semiconductor no. form in such a way that it changes. A method for forming this inclined band layer will be described later. Next, a third semiconductor layer 5 of n-GaAs or undoped GaAs'i is formed. In this case, the concentration of impurities such as Si is 5 x 10”/
cm3 or less. Its thickness is about 50 to 3 (10) A.

Next, a fourth semiconductor layer 6 of p-AlGaAs'fr- having a #A diagonal bandgap is formed. The composition of M is zero at the boundary with the semiconductor 1=s, and is zero at the boundary with the semiconductor 1:7m7, and the M composition continuously changes with the thickness of the pigeon between them. Next, a wide-gap fifth semiconductor layer 7 of p-A and aAs f is formed, and ions such as B and H are added to this multi-layer epitaxial film/bO. Insulation #10i is formed by implantation and separated into first and second regions. Thus, in the first region, a GRIN-SCH sensor is constructed in which the semiconductor layers 3 and 7 are cladding layers, and the zero-order electrodes P and N are respectively formed in the semiconductor layer 8.2. In the second region of the multi-J-epitaxy cell dust circle, an n-type impurity chain acid 9 is formed in a part of the semiconductor 1f 46.7 using an ion implantation method, and brown 1 to third half 4 are formed. 3~5T collector, 4th degree, fifth semiconductor layer 6.7 degrees formed in 9th n-type impurity region 9'! i1' emitter, fourth semiconductor layer 6I7
0B and E constituting a heterojunction bipolar transistor based on the region sandwiched between the emitter and collector of 3.
, CH are base, emitter, and collector electrodes, respectively.

Incidentally, the above-mentioned inclined band structure can be realized by completely changing the ratio of the raw materials during crystal growth. For example, AlGaAs gradient band structure all-organic vapor phase epitaxial method (Metalorganic V
When manufacturing with apor Phase Eptta This method uses a method to change the

FIG. 2 is a band diagram of the HBT having the above-described layered structure in an operating state. The electrons injected into the wide gap emitter 9 are rounded and accelerated by the internal electric field of the base, as shown in the figure, and travel faster than diffusion in a normal uniform base layer.

Boltzmann's constant, T: absolute temperature, q: electron gap), and the difference in the gap in the base layer is expressed as △Eg =
If it is 0.2 eV, the electron transit time τ is about 1/4 of that in the uniform base case.The current amplification factor β of oHBT is proportional to the electron speed at the base no, so as a result β
increases several times. If we create a structure in which β can be large in this way, the base MJ # will change (impurity # degree FJ 5
X 10 (appropriately 7 cm) can compensate for the decrease in β, and the HBT's (I
It becomes possible to increase the speed (II: faster than GHz).

1. Since the quantum well and the inclined band gap on one side become a depletion layer of the collector 1llil, there is no problem in the operation of the HBT. On the other hand, the boundary of the n- impurity region on the emitter side is set at the boundary between the AlGaAs layer of the semiconductor layer 7 and the graded bandgap layer of the semiconductor layer 6, or inside the layer 6. This is because if a pn junction is formed in the semi-conductive layer 7, the HBT's main effects of wide emitter and narrow base will be impaired. That is, the emitter current injection efficiency decreases.

Next, the effect of this structure on LD will be explained.

Does the LD oscillation threshold 1 depend on the optical confinement coefficient F and the active layer gain α? = 1 (α+1 tnl , expressed as 1'
LR will be done. When the active layer is made of a quantum well, the level density of the light emitting level increases, so α increases.0 Also, by making both sides of the active layer a sloped bandgap, the optical confinement coefficient decreases in the case of a normal steep bandgap change. increases, and in addition to the above two effects, it becomes possible to reduce the excavation threshold.
In this series, a beam guide structure is used to further lower the threshold value, and it is predicted that laser operation will be possible with a current of 10 ffIA or less.

Note that isolation between elements is ensured by an insulating layer.

Note that AlGaAs can also be used instead of GaAs for the third semiconductor layer.

Also number 1. Second. 4th. The fifth semiconductor layer may be made of InP, and the third semiconductor layer may be made of InGaAs or InGaAsP. Furthermore, as a semi-insulating substrate, I
nP't'' can also be used.

(Banmei υ effect) According to the uninventiveness of the waterworks, K) It is possible to provide an 0EIC with an element structure that makes it possible to improve the performance of both HBT and LD. The UNA0EIC has the advantage that it can be used as a transmitter for subscriber-based optical communications.

(b) Quantum well structure (impurity I#
The oscillation level is 5 x 10 l7cm'). By increasing the gain and increasing the gain, the decrease in the oscillation threshold current can be reduced by μ, and by creating a sloped bandgap structure on both sides of the active J, the original confinement effect t'4 can be achieved, further reducing the threshold current. Can be done.

C→ In the conventional structure in which the active layer of the above LD is shared with the base layer of t-HBT, the active layer has a retracting well structure, so making it thinner (~0.01 μm) increases the base resistance. However, the HBT has the disadvantage of slow operation speed.

In this regard, in the present invention, by making only one of the two inclined bandgap layers the base t* of 't-HBT, it is possible to avoid making the base layer thinner (~0.2 μrn).

Furthermore, the base layer of the graded bandgap layer tHBT (appropriate impurity concentration of about 5×10”/glue) generates an electric field in the base layer and accelerates carriers.

Due to this acceleration, carriers have a higher diffusion rate than the conventional uniform base (drift speed reduction), and as a result, the current amplification factor can be increased.

(e) It is formed from an all-epitaxial film with a pn structure, which is the basis of an LD, and is used as an emitter by ion implantation or vapor phase diffusion to form an n-type impurity region that reaches into the upper inclined bandgap layer.

Fabricate HBTk with npn structure. This simple process allows the LD, HBT, and ° to be mounted on the same substrate.

(F) Since a medium insulating substrate is used, elements can be separated.

Wiring can be done easily and at the same time, collector capacitance can be reduced, so high-speed operation of the device is possible.

(g) Active layers of I and D (appropriate impurity concentration ≦5 x 1
By setting appropriate impurity concentrations in the HBT base layer (approx. 0',/cm') and the HBT base layer (approx. It also has the effect of increasing the cutoff frequency of the HBT.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the vertical structure of the uninvented device, FIG. 2 is a diagram showing the band structure of the uninvented device, and FIG. 3 is a diagram showing a conventional example. 1...Semi-insulating GaAs substrate 2------- n''-GaAs layer 3... First semiconductor layer, n-At, Ga1-
1As layer 4...Second semiconductor/1, graded bandgap n-AlGaAs5...Third semiconductor 1m, n or undoped GaAs layer 6...
・Fourth semiconductor layer, graded bandgap p-ABGaA
s7...Fifth semiconductor layer, n-At engineering Ga1-
, As layer 8 =---・p+-GaAs)fi9...
...N-impurity region 10...Insulating layer for inter-element separation Patent applicant Nippon Telegraph and Telephone Corporation Figure 2

Claims (12)

[Claims] (1) On a semi-insulating substrate, a first conductivity type wide-gap first semiconductor layer, a first conductivity type second semiconductor layer having a sloped bandgap, and a first conductivity type or narrow gap semiconductor layer to which no impurities are added. A first region in a multilayer epitaxial film in which a third semiconductor layer of , a fourth semiconductor layer of a second conductivity type having a tilted bandgap, and a fifth semiconductor layer of a wide gap of a second conductivity type are sequentially stacked. A GRIN-SCH laser is constructed in which the third semiconductor layer is an active layer and the first and fifth semiconductor layers are cladding layers, and the first to third semiconductor layers are formed in a second region within the multilayer epitaxial film. A heterojunction bipolar transistor in which the layer is the collector, the impurity regions of the first conductivity type formed in the fourth and fifth semiconductor layers are the emitter, and the region sandwiched between the emitter and collector in the fourth semiconductor layer is the base. An optical/electronic integrated circuit characterized by comprising: (2) The opto-electronic integrated circuit according to claim 1, wherein the first conductivity type is n type and the second conductivity type is p type. (3) The first, second, fourth, and fifth semiconductor layers are AlGaA
s. The opto-electronic integrated circuit according to claim 1, wherein the third semiconductor layer is GaAs or AlGaAs. (4) The second semiconductor layer has an Al composition of 0 at the connection part with the third semiconductor layer, and an Al composition of A at the connection part with the first semiconductor layer.
The fourth semiconductor layer is AlGaAs in which the Al composition changes sequentially so that the Al composition is equal to the Al composition of the first semiconductor layer, and the fourth semiconductor layer has an Al composition of 0, The Al composition at the connection part with the fifth semiconductor layer is the fifth
4. The opto-electronic integrated circuit according to claim 3, wherein the optical/electronic integrated circuit is made of AlGaAs whose Al composition changes sequentially so as to be equal to the Al composition of the semiconductor layer. (5) The opto-electronic integrated circuit according to claim 1, wherein the first, second, fourth, and fifth semiconductor layers are InP, and the third semiconductor layer is InGaAs or InGaAsP. . (6) The opto-electronic integrated circuit according to claim 1, wherein the semi-insulating substrate is GaAs or InP. (7) On a semi-insulating substrate, a first conductive type wide-gap first semiconductor layer, a first conductive type second semiconductor layer having a sloped bandgap, a first conductive type or a narrow gap layer to which no impurity is added. A multilayer epitaxial film is formed by sequentially stacking a third semiconductor layer of a second conductivity type with a tilted bandgap, a fourth semiconductor layer of a second conductivity type with a wide gap, and an insulating layer. The multilayer epitaxial film is separated into a first region and a second region, and the third semiconductor layer is used as an active layer and the first and fifth semiconductor layers are used as cladding layers in the first region in the multilayer epitaxial film. GRIN-SCH
A laser is configured, and impurity regions of the first conductivity type are selectively formed in the fourth and fifth semiconductor layers in the second region in the multilayer epitaxial film by using an ion implantation method, and The third semiconductor layer is used as a collector, the first conductivity type impurity regions formed in the fourth and fifth semiconductor layers are used as an emitter, and the fourth semiconductor layer is used as an emitter.
1. A method for manufacturing an opto-electronic integrated circuit, comprising forming a heterojunction bipolar transistor based on a region sandwiched between an emitter and a collector in a semiconductor layer. (8) The method for manufacturing an optoelectronic integrated circuit according to claim 7, wherein the first conductivity type is n type and the second conductivity type is p type. (9) The first, second, fourth, and fifth semiconductor layers are AlGaA
8. The method of manufacturing an opto-electronic integrated circuit according to claim 7, wherein the third semiconductor layer is GaAs or AlGaAs. (10) The second semiconductor layer has an Al composition of 0 at the connection part with the third semiconductor layer, and an Al composition of the second semiconductor layer at the connection part with the first semiconductor layer is equal to the Al composition of the first semiconductor layer. It is AlGaAs whose Al composition changes sequentially, and the fourth
The semiconductor layer is made of Al so that the Al composition at the connection part with the third semiconductor layer is 0 and the Al composition at the connection part with the fifth semiconductor layer is equal to the Al composition of the fifth semiconductor layer. 10. The method of manufacturing an opto-electronic integrated circuit according to claim 9, wherein the material is AlGaAs whose composition changes sequentially. (11) The first, second, fourth, and fifth semiconductor layers are InP,
The optical system according to claim 7, wherein the third semiconductor layer is InGaAs or InGaAsP.
Method of manufacturing electronic integrated circuits. (12) The method for manufacturing an opto-electronic integrated circuit according to claim 7, wherein the semi-insulating substrate is GaAs or InP.