JPS6360571A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To reduce the temperature change of an optical output, and to reduce cost and improve reproducibility by making a refractive index higher than first and second semiconductor layers holding a light-emitting region semiconductor, narrowing forbidden band width, altering forbidden band width in the direction of laminating and doping an impurity as a non-radiative center into a narrow region in the light- emitting region semiconductor. CONSTITUTION:An S-doped n-type InP buffer layer 12, a light-emitting region 15 consisting of an un-doped InGaAsP layer 13 and an Fe-doped InGaAsP layer 14, a Zn-doped p-type InP clad layer 16, and a Zn-doped p-type InGaAs cap layer 17 are laminated onto an S-doped n-type InP substrate 11 in succession, p-n-p structure 18 normally used for current constriction to the substrate is laminated around the lightemitting region 15, and electrodes 19 are shaped onto an upper surface and a lower surface. Both a conduction-band lower end and a valence-band upper end intermittently vary regarding the direction of laminating in the forbidden band width of the light-emitting region 15 at that time, and an impurity forming a non-radiative center is doped only to the layer 14 having narrow forbidden band width. Accordingly, reproducibility is improved and cost can be reduced while the temperature dependency of an optical output is also minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor light emitting device whose light output has small temperature fluctuations.

(Prior Art) It is a serious practical problem that the light output from a semiconductor light emitting device fluctuates depending on the ambient temperature. In semiconductor lasers,
To reduce this problem, changes in the carrier density distribution in ultrathin films due to quantum size effects are used to reduce temperature changes in the carrier density distribution. phys,
Lett, ) 1980, Vol. 36, p. 19).

(Problem to be solved by the invention) However, using this ultra-thin film structure
Although it has a great effect on s-based materials, it is not easy to apply it to other material systems. In particular, with semiconductor materials containing KP (phosphorus), the production of ultra-thin film structures itself is extremely difficult, and although it is possible to reduce temperature fluctuations in optical output, it is impossible to make them extremely small. There are also problems with the reproducibility and cost of device manufacturing.

(Means for Solving the Problems) A semiconductor light-emitting device according to the present invention has a multilayer heterostructure; this multilayer heterostructure includes a semiconductor layer that serves as a light emitting region with first and second semiconductor layers having different conductivity types. This light-emitting region semiconductor has a higher refractive index and a narrower forbidden band width than the first and second semiconductor layers; In the light-emitting region semiconductor, the forbidden band width changes with respect to the stacking direction and the forbidden band width increases. is characterized in that a relatively narrow region is doped with an impurity that serves as a non-emissive center.

(Function) When the forbidden band width of the semiconductor light emitting region is changed in the stacking direction, the injected carriers are concentrated in the region where the forbidden band width is narrow, especially in a low temperature state.

On the other hand, when the temperature rises from this state, the range of the carrier energy distribution widens, so that it also spreads toward the wide forbidden band width region in the stacking direction. Here, if an impurity serving as a non-luminescent center is intentionally doped in a region with a narrow forbidden band width, radiative recombination of carriers is relatively reduced in this region. However, in this structure, the influence of non-luminous centers is large at low temperatures, where luminous efficiency is generally high, but as the temperature rises and the luminous efficiency decreases, the energy distribution of the carriers widens. Since the spatial distribution in the stacking direction is also widened, the influence of non-emissive centers is smaller than K. As a result, it is possible to suppress fluctuations in the optical output over a wide temperature range under a certain carrier injection state. In this case, the light output at low temperatures is somewhat reduced due to this effect, but the reduction in light output at high temperatures is small, and in actual use, the system must be tailored to the characteristics at the highest temperature in the operating temperature range. There is no problem in thinking. Furthermore, by selecting the manner in which the forbidden band width of the semiconductor light emitting region changes and the degree of doping of impurities that serve as non-light emitting centers, it is possible to make the temperature dependence of the optical output extremely small.

This structure does not require precise control of film thickness during manufacturing, so it can be applied to many material systems, and it can be realized without special manufacturing methods, so it is excellent in cost and reproducibility.

(Example) The present invention will be described in more detail below with reference to the drawings.

FIG. 1(a) is a sectional view in the stacking direction of a light emitting diode according to the first embodiment of the present invention, FIG. 1(b) is a perspective view thereof,
FIG. 1(C) is a band diagram of the light emitting region. In this example, an S-doped n-type InP substrate was grown using a vapor phase growth method.
a 2 μm S-doped n-type InP buffer layer 12.
5ooA's undove error rr G a A s P (
Forbidden band width α98 eV) Fe-doped layers 13 and 300^ Q a A s P (Forbidden band width 0.96 e
V) Zn of light emitting region 15.2/jm consisting of layer 14
Doped p-type InP cladding layer 16 and α5 μm Z
n-doped p-type I no, sa Ga O, 47As
A cap layer 17 is sequentially laminated, and a p-n-p structure 18, which is usually used for current confinement, is formed on this substrate with a width of 1.5 μm.
The electrodes 19 are formed around the light emitting region of m by a liquid phase growth method, electrodes 19 are formed on the upper and lower surfaces, and after separation, a non-reflective layer (2) IA is formed on one end surface.

The other end surface is coated with high reflection (2) IB.

Here, the forbidden band width of the light emitting region is the lower limit of the conduction band IC.

The valence band upper end ID also changes intermittently with respect to the stacking direction, as shown in FIG.
Fe, which is an impurity that forms non-luminescent centers only, is doped at a concentration of about 1016 cm-3.

In this example, the optical output when the injection current is 80 mA is:
Temperature fluctuations in optical output were small, with 1 mW at 20°C and 0.8 mW at 70°C.

Next, a light emitting diode according to a second embodiment of the present invention will be described. This has almost the same laminated structure and device structure as the first embodiment, but the semiconductor light emitting region 15 is 200^
The undoped InGaAsP (forbidden band width α98 eV) layer 13 and the 50^ Fe-doped InGaAsP (forbidden band width α96 eV) layer 14 were laminated in five alternating periods.

In this example, the temperature dependence of the optical output was almost the same as in the first example, and the shape of the optical output beam was also good and symmetrical with respect to the stacking direction.

Next, a semiconductor laser according to a third embodiment of the present invention will be described. Figure 2(a) is a cross-sectional view in the stacking direction;
b) is a perspective view thereof, and FIG. 2(c) is a band diagram of its light emitting region. In this third embodiment, Si-doped n-type Ga
On the S substrate 21, a 1 μm Si-doped n-type Ga A
s buffer layer 22.2μm SI doped n-type A 10
．． 3G a O, 7A s cladding layer 23.1 The composition ratio changes continuously from O to α1, and Fe is doped only in the region 24 where the Aft composition ratio is O to 100^, and the thickness is α1 μm. A i xG a 1 +, Zn-doped p-type A fio with As light emitting region 25.2 μm, 3G
a O,7A s cladding layer 26 and 0.5 μm Z
An nn-doped GaAs cap layer 27 is laminated in the 11th order, and 5io2 is deposited on the top surface of the laminated layer using the CVD method, and a strip-like 5i02 layer with a width of 1.5 μm is selectively left by IJ mesogelation method. up to 1.5μ
Both sides of the striped region of m@ are etched to form a p-n-p structure 28 A10.3 Ga for current confinement.
After stacking 5 layers of O,7A and removing SiO2, the top surface
The electrode 29 is manufactured by vapor deposition on the lower surface.

In this third embodiment, the forbidden band width of the light-emitting region changes continuously in the stacking direction, and the pe that forms the non-light-emitting center only in the region 24 where the forbidden band width is relatively narrow is approximately 101.
It is doped with a concentration of 6-1017 cm-3.

The actual device characteristics are that the oscillation threshold current value is about 40 mA at both 20°C and 70°C, and it hardly changes depending on temperature, and the optical output when the injection current is 80 mA is 20 mA.
It was approximately 15 rnW both at 70° C. and 70° C., and was excellent in extreme pressure.

Although three embodiments have been described above, the present invention is not limited to these embodiments in any way. For example, the semiconductor growth method may be a liquid phase growth method, a molecular beam epitaxy method, etc., and the impurity to be doped may be anything other than Fe as long as it forms a non-luminescent center, for example, Cr%.
It may be V (vanadium) or a composite thereof. Furthermore, the band structure of the light emitting region is also the lower conduction band I
C.

The valence band toe ID may change continuously in a parabolic manner as shown in Figure 3 (a), or it may change intermittently in a stepwise manner as shown in Figure 3 (b). good.

(Effects of the Invention) According to the present invention, a semiconductor that does not require strict film thickness control and has a simple device manufacturing process, is advantageous in improving reproducibility and reducing costs, and has a small temperature dependence of optical output. A light-emitting device is obtained, and from this K, an optical communication system and an optical information processing system that operate stably even under fluctuations in ambient temperature without using a complicated temperature stabilizing device or an expensive semiconductor light-emitting device can be realized. Can be done.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view in the stacking direction of a light emitting diode according to a first embodiment of the present invention, FIG. 1(b) is a perspective view thereof, and FIG. 1(c) is a band diagram of its light emitting region. Figure 2 (a
) is a cross-sectional view in the stacking direction of a semiconductor laser according to a third embodiment of the present invention, FIG. 3B is a perspective view thereof, and FIG. FIGS. 3(a) and 3(b) are band diagrams showing other examples of the band structure of the light emitting region. 11...n-type InP substrate, 12...n
type InP buffer layer, 13...undoped I
flGaASP (forbidden band width α98 eV) layer, 14...
...Fe-doped En Qa As P (forbidden band width α96 eV) layer, 15-... Light emitting region, 16.
...p-type InP cladding layer, 17 ・'-”'
f) Type I nO, 53Qa O, 47As cap layer-
18...p-n-p structure, 19...electrode, IA...non-reflective), IB...
High reflective coating, IC...lower end of conduction band, ID...
...Top of valence band, 21...n-type QaAs
Substrate, 22...n-type QaAs buffer layer, 2
3-... n-type A1o, a Qa O, 7A s cladding layer, 24... Fe-doped 1 in the light emitting region
00A region, 25-...1xGa, -xAs light emitting region, 26...p-type A n O, 3G ao
, 7 A s cladding layer, 27...p-type layer aA
S cap layer, 28... p-n-p structure, 29
······electrode. Agent Patent Attorney Shinsuke Honjo Figure 1 (a) Figure 1 (b) Figure 1 (c) Figure 2 (a) Figure 2 (1)) ALxGa+-x As L Kusa Ori 5 Big Purchase Figure 2(c)

Claims (1)

[Claims] It has a multilayer heterostructure; this multilayer heterostructure includes a semiconductor serving as a light emitting region sandwiched between first and second semiconductor layers having different conductivity types; this light emitting region semiconductor is
and the second semiconductor layer, the refractive index is higher and the forbidden band width is narrower; in the light emitting region semiconductor, the forbidden band width changes with respect to the stacking direction, and impurities that become non-emissive centers are present in the region where the forbidden band width is relatively narrow. A semiconductor light emitting device characterized in that it is doped.