JPS63129678A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve light emitting efficiency, by providing a region whose refractive index is smaller than that in a well layer in a quantum well structure, at the outside of the quantum well structure, and forming a light confining layer. CONSTITUTION:On a substrate 1, a collector layer 2, a base layer 3, a quantum well structure 4, an emitter layer 5 and a semiconductor layer of an emitter contact layer 6 are provided. An emitter electrode 7, base electrodes 8 and a collector electrode 9 are formed. In the quantum well structure 4 provided between the reverse conductivity type emitter region and the base region, electrons and holes can undergo resonant tunneling at the same time. A region whose refractive index (c) is smaller than that in a well layer 4W in the quantum well structure is formed in the vicinity of an interface between the emitter region and the base region at least one quantum well structure 4. Light is guided in said region. Thus the efficiency of the light emitting function can be improved.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a semiconductor device having a light emitting function, which is provided with a quantum well structure between an emitter region and a base region in which electrons and holes can be simultaneously tunneled resonantly. By providing a region outside the quantum well structure in which the area is smaller than the well layer of the quantum well structure, an optical confinement structure is formed to guide light and improve efficiency.

[Industrial application field]

The present invention relates to an improvement in a semiconductor device utilizing resonant tunneling effect, which was filed by the applicant of the present patent on October 22, 1986.

This semiconductor device realizes an electronic device and an optical device using the same element or the same semiconductor layer structure, and is expected to be applied to optoelectronic integrated circuit devices (OEIC) and the like.

[Conventional technology]

Semiconductor devices such as resonant tunneling bipolar transistors (RBTs) that utilize the resonant tunneling effect have new functions and high speeds that cannot be obtained with conventional ordinary semiconductor devices. It has a structure as illustrated in the schematic side sectional view of FIG. 3(a) and has a light emitting function.

In the conventional example shown in the figure, the impurity concentration is, for example, 6×10”c.
On a type 1 gallium arsenide (GaAs) substrate 41 of about m-' size, there are semiconductor layers 42 to 46 configured as shown below, 47 is an emitter electrode, 48 is a base electrode,
49 is a collector electrode.

Semiconductor layer Composition Impurity Thickness cm-' plane 46 emitter contact N GaAs
n”-6x10+s 20045 layer GaAs n-5X 10”
10045a Spacer layer GaAs Non-doped 544 Quantum well structure 44B Barrier layer A18S Non-doped 24
Senkuru layer GaAs non-doped 544
8 barrier layer AlAs non-doped 243
a spacer layer GaAs non-doped 20
43 base layer GaAs p+-5X 10”
20042 collector layer GaAs n
-I
Doped impurities such as beryllium (Be), n-type G
The impurity of the aAs emitter layer 45, for example, silicon (St)
are inserted to prevent impurity scattering effects on electrons and holes by diffusing into the AlAs barrier layer 44B, respectively, and in the completed semiconductor device, the p + type GaAs base layer 43 and the n type GaAs emitter layer are inserted, respectively. It functions in unison with 45.

Base input voltage V! of this conventional example! The energy band diagram is shown in Figure 3 (b
1, electrons e and holes undergo resonance tunneling together, and the electron and hole concentrations in the well Ji44W become high, where the electrons and holes recombine to generate light hv. This light can be modulated at extremely high speeds due to the characteristics of this type of semiconductor device, and is suitable for high-speed optical communications.

Furthermore, depending on the applied voltage, it is possible to operate the device as a normal RBT without emitting light, so the above-described semiconductor device is extremely convenient for the configuration of an 0BIC.

[Problem that the invention seeks to solve]

The refractive index distribution of the conventional example is shown in FIG. 3(C). The IAs barrier layer 44B sandwiching the well layer 44- which is the light emitting region of this conventional example is the GaAs well layer 44-.
It is suitable for an optical confinement layer in that it has a smaller refractive index, but
Since its thickness is as small as, for example, 2 nm, it cannot function as an optical confinement layer. This AlAs barrier jW44B
It is impossible from the point of view of resonant tunneling probability to make the value more than about 1100n, at which the effect of the optical confinement layer can be obtained.

It is desired to form a light confinement layer in this semiconductor device while maintaining the resonant tunneling probability, and to configure a waveguide that guides the generated light to the end face of the semiconductor substrate, and to improve the luminous efficiency as an edge-emitting type semiconductor light-emitting device. ing.

[Means for solving problems]

The problem is that a quantum well structure is provided between an emitter region and a base region of mutually opposite conductivity types, in which electrons and holes can resonantly tunnel at the same time at the same base voltage. This problem is solved by a semiconductor device according to the present invention, in which a region having a refractive index smaller than that of the well layer of the quantum well structure is formed near the interface with at least one of the regions and the quantum well structure.

[For production]

The semiconductor device according to the present invention includes a quantum well structure in which electrons and holes can be resonantly tunneled simultaneously at the same base voltage between an emitter region and a base region of opposite conductivity types, and performs the light emitting operation as described above. can be done, but
An optical confinement structure is constructed by making the refractive index of at least one of the emitter region and the base region in the vicinity of the interface with the quantum well structure smaller than that of the well layer of the quantum well structure which is the light emitting region.

The emitter region and the base region have a forbidden band width that is at least near the interface with the quantum well structure, so that electrons and holes in the quantum well structure can resonantly tunnel at the same time at the same base voltage. It is necessary to satisfy conditions such as the difference between the resonance levels of the refractive index being equal to or less than the above-mentioned refractive index condition.

〔Example〕

The present invention will be specifically explained below using examples.

FIG. 1 shows a first embodiment of the present invention, in which FIG. 1A is a schematic side sectional view, FIG. 1 is an energy band diagram, and FIG. 1C is a refractive index distribution diagram.

In this example, the impurity concentration is, for example, 6 XIO"cm-'
For example, semiconductor layers 2 to 6 as shown below are provided on a type 1 GaAs substrate 1 of about 100 mL, with 7 being an emitter electrode, 8 a base electrode, and 9 a collector electrode.

However, in the base layer 3 of this example, the forbidden band width and refractive index of In6.5Ali and sAs mixed crystals, which cause lattice mismatch with the GaAs substrate, are realized by an InAs/AlAs strained superlattice structure. .

Furthermore, the emitter layer 5 is approximately 70 mm from the interface with the barrier layer 4B.
GaAs to A10.nmO. ,,Gao, ? The composition ratio is graded up to S to give a gradient to the forbidden band width near the interface with the quantum well structure, and an optical confinement layer having a lower refractive index than the well layer is formed very close to the interface.

Semiconductor layer Composition Impurity Thickness 111-
30m 6 Emifuke contact layer GaAs
nj-6X 10” 200aAs (about 5 nm near 4B is grown without doping) 4 Quantum well structure 4B barrier layer 8 IAs Non-doping 2
4-well layer GaAs non-doped 54
B barrier layer AlAs non-doped 23 hess layer strained superlattice structure 50 periods AlAs p"-5X 10'" 2In
As p+-5X 10” 2 (5 periods near 4B are grown without doping) 2 collector NGaAs
n-lXl01?500 The forbidden band width and refractive index of each of these semiconductor layers are approximately as shown below and in Figure 1 ('b) and (C
This is Mr. 1O.

Semiconductor composition Forbidden band width (eV) Refractive index Ga
As 1.44 3.655
Alo, 3Gao, 7^s 1.79
3.300AIAs 2.1
6 3.1781no, 5A1o, sAs mixed crystal 1.35 3.340 Figure 2 shows a second embodiment of the present invention, Figure ta) is a schematic side sectional view, Figure (b) is an energy band diagram, Figure (C) is a refractive index distribution diagram.

In this example, the impurity concentration is, for example, 6 XIO"cm-3
For example, the following semiconductor layers 22 to 26 are provided on a Y-shaped indium phosphide (InP) substrate 21 of approximately
is an emitter electrode, 28 is a base electrode, and 29 is a collector electrode.

Semiconductor layer Composition Impurity Thickness CIlCl
ll-3 ri emid contact layer 1nGaAsP
n-6xlQll' 20025 Mitsuta layer 1
no, szz^1o, 1aAs n-5X101ff1
00 (approximately 5 nm near 24B is grown without doping) 24
Quantum well structure 24B barrier layer AlAs non-doped
224W well Ji Ga As non-doped 524B barrier layer AlAs
Non-doped 223 base layer 1no, 5zAlo
, 41AS p+-5X 10'" 200 (
Approximately 20nn+ near 24B is grown without doping) 22 Collector II Ir, , 5zA1o, 411AS
n - I , for example, InAs/A with each layer having a thickness of about 2 nm.
Similar results can be obtained with the lAs superlattice structure.

In each of these examples, as seen in each refractive index distribution diagram,
An optical confinement region with a smaller refractive index is formed near the well layer 4-324-, which is the light emitting region, and the light is guided toward the end surface of the semiconductor substrate by this optical confinement region, increasing the efficiency of output light. is significantly improved over the conventional example which does not include an optical confinement region.

As seen in each energy band diagram, the emitter region and the base region of each embodiment satisfy the condition that electrons and holes can simultaneously resonantly tunnel through the quantum well structure at the same base voltage.

〔Effect of the invention〕

As explained above, the semiconductor device of the present invention has the original characteristics that a light emitting device and an electronic device RBT can be obtained with the same element or the same semiconductor substrate configuration, and that extremely high speed modulation is possible as a light emitting device. In addition, it becomes possible to waveguide the light generated in the well layer and obtain optical output with high efficiency, which has a great effect on the development of 0EIC and the like.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the first embodiment, Fig. 2 is a diagram showing the second embodiment, and Fig. 3 is a diagram showing a conventional example. Figure (b) is an energy band diagram, and Figure (e) is a refractive index distribution diagram. In the figure, 1.2 is the semiconductor substrate, 2.22 is the collector layer, and 3 is the refractive index distribution diagram.
．． 23 is the base layer, 4.24 is the quantum well structure, 4B
, 24B is a barrier layer, 4W, 24 is a well layer,
5.25 is an emitter layer, 6.26 is an emitter contact layer, 7.27 is an emitter electrode, 8.28 is a base electrode, 9.
29 indicates a collector electrode. Leather 1 theory fヂ°1 Leather 1 figure $2 figure

Claims (1)

[Claims] A quantum well structure is provided between an emitter region and a base region of mutually opposite conductivity types, in which electrons and holes can be resonantly tunneled simultaneously at the same base voltage, the emitter region and the base region. A semiconductor device characterized in that a region having a refractive index smaller than that of a well layer of the quantum well structure is formed near an interface with at least one of the quantum well structures.