JPH0448622A - Method for doping iii-iv compound semiconductor layer with carbon - Google Patents

Abstract

PURPOSE:To easily control the quantity of doping with carbon by using a group III metal and metal oxide of group III metal as group III material, and controlling the supply ratio to a substrate of them and the temperature of the substrate. CONSTITUTION:If carbon is used as dopant, the quantity of dopant increases sharply as compared with the case where beryllium is used as dopant. This is attributable to that carbon is restrained from entering between lattices since the atoms are somewhat large in contrast to that beryllium sometimes enter between lattices resulting from the atoms being small, etc. In addition, by controlling the ratio of the quantities of group III metal and the metal oxide of group III metal both supplied to a substrate, the supply ratio to group III metal of carbon can be adjusted, and besides by controlling the temperature of the substrate, the intake of carbon can be adjusted. From these reason, the quantity of doping a III-IV compound semiconductor layer with carbon can be controlled easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for doping carbon into a ■-■ group compound semiconductor layer formed in a semiconductor laser or the like.

[M] In the preparation of the group I [1-IV compound semiconductor layer]
A BE method (molecular beam growth method) or the like is used, and beryllium (Be) is used as the P-type dopant in this case. The control of this Be doping amount is as follows:
This was mainly done by loading Be and controlling the temperature of the crucible.

Here, when an electrode is formed on a semiconductor layer, contact resistance occurs at the interface.This contact resistance is determined by the contact area between the semiconductor layer and the electrode, and depends on the carrier concentration of the semiconductor.

However, depending on the application of the semiconductor device, it is necessary to reduce the above-mentioned contact area. Therefore, in order to prevent the electrical characteristics of the semiconductor device from deteriorating, it is necessary to increase the carrier concentration of the semiconductor.

However, when Be is used as a dopant as in the above conventional method, the carrier concentration is IQ "Cl-3
It can only be doped to a certain extent.

As a result, the contact resistance cannot be lowered, resulting in a problem in that the electrical characteristics of the semiconductor device deteriorate.

The present invention has been made in view of the current situation, and is capable of suppressing an increase in contact resistance at the interface between an electrode and a semiconductor layer even when the contact area is reduced.
An object of the present invention is to provide a method for doping carbon into an r-IV group compound semiconductor.

In order to achieve the above object, the present invention provides a carbon doping method for crystal growth of a ■-■ group compound semiconductor layer on a substrate, which comprises using a group ■ metal and a group ■ metal as a group ■ raw material. The present invention is characterized in that the amount of carbon doped is controlled by controlling the supply ratio of these metal organic substances to the substrate and the temperature of the substrate.

In the above doping method, carbon produced by decomposition of a metal organic substance is used as a P-type dopant. When carbon is used as a dopant in this way, the amount of doping increases dramatically compared to when beryllium is used as a dopant. This is because, in the case of beryllium, the atoms are small and may invade the interstitial space, whereas in the case of carbon, the atoms are somewhat large, so they are inhibited from penetrating into the interstitial space. This is thought to be due to the fact that

In addition, with the above method, by controlling the supply ratio of the group (III) metal and the metal organic substance of the group (III) metal to the substrate, it is possible to adjust the supply ratio of carbon to the group (III) metal, and The amount of carbon taken in can be adjusted by controlling the temperature.

For these reasons, it becomes possible to easily control the amount of carbon doped into the III-IV group compound semiconductor layer.

Sue” 1-1 doctor One embodiment of the present invention will be described below.

〔Example〕

A mesa semiconductor laser (cavity length: 2
The structure has a Si-doped GaAs buffer layer (0.7 μm) on an n-type GaAs substrate, an n-Alo,
4Gao, 6A5 cladding layer (1 μm), undoped GaAs active layer (500 layers), p-Alo, 4
Ga0. bAs cladding layer (1 μm) and p-GaA
The structure is such that an S ohmic contact layer (0.3 μm) is formed in this order, and electrodes are formed on the surfaces of the n-type GaAs substrate and the p-GaAs ohmic contact layer.

Here, when manufacturing the mesa semiconductor laser having the above structure, an MBE apparatus was used. This MBE equipment uses four metal raw materials [gallium (Ga), aluminum (/l),
It has a cell and a crucible for heating arsenic (As) and silicon (Si), and a nozzle for introducing an organic metal (trimethyl gallium (TMG)) using a carrier gas (H2).

In addition, in the above device, the molecular beam intensity supplied to the substrate is controlled by the temperature of each cell for metal raw materials, and T
In MG, it is controlled by the flow rate of carrier gas.

Further, whether or not each molecular beam was supplied to the substrate was determined by opening and closing a shutter provided facing each cell.

Next, a method for manufacturing a mesa semiconductor laser using the above MBE apparatus will be described.

First, using an MBE device, S was deposited on an n-type GaAs substrate.
i-doped GaAs buffer layer, n-AIo, aGa
, 6As layer, undoped GaAs active layer, and p-AlolGao.

A 6As cladding layer and a p-GaAs ohmic contact layer are grown. The growth conditions at this time are as follows.

■SiSi-doped GaAs buffer layer Undoped GaA
sGrowth conditions up to the active layer.

(1) Substrate temperature: Tsi680'c (2) Metallic Ga molecular beam intensity: F,, == 8X
10-'torr(3)A/2 molecular beam intensity: FAa-
1,5X 10-'Lorr(4)As molecular beam intensity:
F As = I
ao, = Growth conditions (1) to (4) for the As cladding layer are the same as those in ① above, and in addition, TMC, is changed to TMG molecular beam intensity Ft, 1a -2X 10 by using H2 gas.
■Growth conditions for p-GaAs ohmic contact layer (1) T! -600°C (2) F tsc = 5 x 10-6torr
(3) F as = I X 10-'torr above ■
In the case of ■, FG and FTM. and T,
By controlling the p-type carrier concentration, it is possible to change the p-type carrier concentration. That is, by increasing the proportion of FTM or by lowering T, it is possible to increase the amount of doping, while by decreasing the proportion of FTM or by increasing T, the amount of doping can be increased. It becomes possible to reduce the

Specifically, in the case of ■■ above, p-AI. , aGao
, the carrier concentration of the hAs cladding layer is 5×10
``C!l-'', and the carrier concentration of the p-GaAs ohmic contact layer is 2×102°Cl-3.

Next, the growth wafer produced by the above method was coated with n-Alo, aGao, 6As cladding layers (
This layer was removed by etching to a depth of 0.2 μm. After this, the n-type GaAs substrate and p
-An electrode was formed on the surface of the GaAs ohmic contact layer. In this way, a mesa semiconductor laser with a cavity length of 250 μm was manufactured.

The semiconductor laser manufactured in this way will be referred to as the (A) laser hereinafter.

[Comparative example]

A semiconductor laser having the same structure was fabricated using a conventional Be-doped growth method.

The semiconductor laser manufactured in this manner will be referred to as an (X) laser hereinafter.

〔experiment〕

The I-■ characteristics of the laser (A) of the present invention and the laser (X) of the comparative example were investigated, and the results are shown below.

As a result, in the (X) laser, the voltage at a current value of 30 mA is 2.3-2.5cm, while in the (A) laser, the voltage at the same current is 1.9-2. It is recognized that the OV has decreased significantly. therefore,
It can be seen that the (A) laser is dramatically improved compared to the (:0 laser).

This is considered to be due to the fact that the (A) laser has a larger amount of P-type dopant doping than the (X) laser.

According to the present invention as described above, the amount of doping can be dramatically increased and the amount of doping can be easily controlled. Therefore, even when the contact area between the semiconductor layer and the electrode is reduced, it is possible to suppress an increase in contact resistance at these interfaces.

In addition, since carbon is not a harmful substance like beryllium, it also has the effect of improving work safety during manufacturing.

Procedures (Published by Fusho Seishin) November 2, 1990 1990 Patent Application No. 156561 2, Title of Invention: Carbon doping method for m-v group compound semiconductor layer 3, Amendment case Related Patent Applicant Address 2-18 Keihan Hondori, Moriguchi City Name (188) SANYO Electric Co., Ltd. Patent Applicant: SANYO Electric Co., Ltd.

Claims (1)

[Claims] (1) A carbon doping method for crystal growth of a group III-IV compound semiconductor layer on a substrate, which method uses a group III metal and a metal-organic substance of the group III metal as group III raw materials, and 1. A method for doping carbon into a group III-IV compound semiconductor layer, the method comprising controlling the amount of carbon doped by controlling the supply ratio of carbon and the temperature of the substrate.