JPS62269387A - Manufacture of semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To make the tail portions of a density distribution semi-insulative and avoid the leakage of electric current by specifying a donor impurity density which produces conduction electrons as well as an acceptor imprurity density that makes semiconductor layer semi-insulative and perform doping. CONSTITUTION:In the case of BH laser that makes buried semiconductor lasers 6 semi-insulative, a density distribution of acceptor impurity that performs thermal diffusion from a p<+> contact layer 5 and p-type confinement layer 4 to the buried layers 6 is composed of a shallow high density area 7s that is confined within the vicinity of interface and an area 7t of low density distribution that is called tail of its area and is deeper than 7s and yet above density distribution permits most of leaked electric current IL to flow through the railed area 7t. Thus, on the occasion of epitaxial growth of the buried semiconductor layers that are in a semi-insulative state, a relation between a maximum density Na in the area of 7t of the density distribution of diffused acceptor impurities and a density Nd of donor impurities that develop conduction electrons is shown by Nd.Na and further, the relation between the above Nd and an acceptor impurities density Nt that forms deeper level is shown by Nt>Nd. The above state causes the conduction electrons in all areas including ranges that are not under the influence of acceptor impurities thermal diffusion to be in a semi-insulative area by trapping.

Description

[Detailed Description of the Invention] C-Summary] This invention provides a semiconductor light emitting device in which when the maximum concentration in the tail portion of the concentration distribution of acceptor impurities thermally diffused during the manufacturing process into a semiconductor layer embedding an active region of a semiconductor light emitting device is Na, Toner impurities (concentration N) that generate conduction electrons in the semiconductor layer
d) and an acceptor impurity (fIIi degree Nt) that forms a deep level that makes the semiconductor layer semi-insulating, with Nt>N
By doping so that d>Na, the tail portion also becomes semi-insulating to prevent leakage current and improve characteristics such as dark value current and efficiency.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor light emitting device, and more particularly to a method of manufacturing a semi-insulating buried layer of a semiconductor light emitting device having a buried structure.

In optical communications and other systems that use light as a medium for information signals, semiconductor light emitting devices play an extremely important role as light sources that generate optical signals.

Therefore, in order to advance the sophistication and diversification of these systems, there is a demand for further improvements in characteristics such as dark value current and efficiency of semiconductor light emitting devices, particularly lasers.

[Conventional technology]

For example, an indium phosphide/indium gallium arsenide fi (InP/InGaAsP)-based semiconductor laser whose wavelength band is approximately 1.3 to 1.6 μm11 suitable for transmission through a silica-based fiber for optical communication is shown in a schematic side cross-sectional view in Fig. 4. B) I
re) lasers are known.

InP/InGaAsP with semi-insulating buried layer
For example, the old type router is (100) of the n-type 1nP substrate 21.
A heterojunction stacked structure consisting of an n-type 1nP confinement layer 22, an InGaAsP active layer 23, an n-type 1nP confinement layer 24, and a p'' pear-shaped 1nGaAsP contact layer 25 epitaxially grown on the surface is mesa-etched so that the length direction is (011 ) direction is formed, and a semi-insulating InP layer 26 is buried and grown in this etched region.Note that 28 is a p-side electrode and 29 is an n-side electrode.

In this conventional example, the semi-insulating 1nP buried layer 26 is made of iron (Fe), chromium (Cr), etc. for the purpose of current confinement and refractive index guiding to control the transverse moat of the laser beam.
The conduction electrons are trapped by deep units obtained by doping with transition elements such as, making it semi-insulating.

[Problem that the invention seeks to solve]

It is expected that good current confinement will be achieved by making the buried layer of the BH laser a semi-insulating semiconductor layer as described above, but in reality, the leakage current IL in the path shown by the arrow in Fig. 4 is expected to be realized.
This causes an increase in dark value current and a decrease in efficiency.

This leakage current IL is caused by zinc (Z) due to heating during epitaxial growth and electrode formation process.
n), p heavily doped with cadmium (Cd), etc.
+ InP made semi-insulating by the above method from the current 1nGaAsP contact layer 25 and the n-type 1nP confinement layer 24
This is because these acceptor impurities diffuse into the buried layer 26 and provide p-type conductivity.

In order to improve the basic characteristics such as dark value current and efficiency of the B) I laser with a semi-insulating semiconductor layer buried structure,
It is essential to sufficiently suppress this leakage current, and a manufacturing method that achieves this is strongly desired.

[Failure to solve the problem]

The problem is that a semiconductor layer embedding the mesa region of a semiconductor substrate in which a striped mesa region including an active layer and confinement layers of opposite conductivity types is formed is inserted into the semiconductor layer from the semiconductor substrate during the manufacturing process. The maximum concentration in the tail of the concentration distribution of the diffused acceptor impurity is Na
According to the present invention, the concentration Nd of the donor impurity that generates conduction electrons and the concentration Nt of the acceptor impurity forming a deep level that makes the semiconductor layer semi-insulating are set to Nt>Nd>Na. The problem is solved by a method for manufacturing a semiconductor light emitting device.

[For production]

As shown in FIG. 1, in a BH relay in which the buried semiconductor layer 6 is semi-insulating, the concentration distribution of acceptor impurities thermally diffused from the p+ type contact layer 5 and the p-type confinement layer 4 into the buried layer 6 during the manufacturing process is as follows. As shown in FIG. 2, an example of the hole concentration distribution consists of a shallow high-concentration region 7S limited to the vicinity of the interface, and a deeper, low-concentration region 7t called a tail. In the region 7s, impurity atoms replace the crystal lattice, and in the low concentration tail region 7t, the impurity atoms are thought to have entered between the crystal lattices, but the leakage current 1. Most of it passes through this low concentration tail region 7t, as shown by the arrow.

According to the present invention, when epitaxially growing a buried semiconductor layer to make it semi-insulating, this semiconductor layer is doped not only with an acceptor impurity that forms a deep level that makes it semi-insulating, but also with a donor impurity that generates conduction electrons. With respect to the maximum concentration Na in the tail region 7t of the concentration distribution of acceptor impurities diffused during the manufacturing process, the conductivity type of this tail region 7L is inverted as the concentration Nd of donor impurities that generate conduction electrons is greater than Na, and further The concentration of acceptor impurities forming a deep unit is set to Nt>Nd, and conduction electrons are trapped in the entire region including the range where thermal diffusion of the acceptor impurities does not reach, thereby making the region semi-insulating.

As a result, the buried semiconductor layer becomes entirely semi-insulating, except for the heavily doped diffusion region 7S in the very vicinity of the p-type region 4.5 of the semiconductor substrate to be buried, thereby preventing leakage current.

〔Example〕

The present invention will be specifically explained below using examples.

FIGS. 3(a) to 3(di) are schematic side sectional views in order of steps showing an embodiment of the present invention.

Figure 3 (see al = For example, tin (Sn) is added to the (100) plane of the n-type 1nP substrate 1 at a concentration of IXl0111c+o
An n-type 1nP confinement layer 2 doped to about -' and having a thickness of about 3, for example, 0.15μ thick, undoped and having a luminescence peak wavelength of 1.3. um InGaAsP active layer 3
For example, an n-type 1nP confinement layer 4 doped with Cd to a concentration of about 5XIO1ffCm-' and a thickness of about 1.5 μm, and a p4-type confinement layer 4 doped with Zn to a concentration of about 1×1019 cm-3 and a thickness of 0.5 μm, for example. 1nGaAsP contact layer 5
are sequentially grown epitaxially.

A mask 11 for forming a stripe region is formed using, for example, silicon dioxide (SiO□) or the like to have a width of about 2.5 to 3 μI in the (011) direction on the surface of the semiconductor substrate.

FIG. 3 (see bl: This semiconductor substrate is, for example, bromine (B
r) - Etching is performed using a methanol solution to form an inverted mesa-shaped stripe region.

FIG. 3 (see C1) A semi-insulating 1nP buried layer 6 is epitaxially grown by, for example, vapor phase epitaxy (VPE method), metal organic pyrolysis vapor phase epitaxy (MO-CVD method), or the like.

The maximum concentration Na in the tail region of the concentration distribution of acceptor impurities diffused into the InP buried layer 6 during the manufacturing process of this embodiment
is about 10IbcI11-3 or less, and when sulfur (S) is used as a toner impurity, Nd=2XIO"am-
For example, Pe is doped as an acceptor impurity to form a unit with a depth of about 3.3 mm or more.

See FIG. 3+d+: Next, the mask 11 is removed, the n-side electrode 8 and the n-side electrode 9 are formed, and the device of this example is completed through processes such as crease formation.

In this embodiment, a dark value current of about 10 mA and an external differential efficiency of about 60% in the rated operating state are obtained, whereas in the corresponding conventional example, for example, a dark value current of 20 m^ and an external differential efficiency of about 40% are obtained. A clear improvement has been demonstrated compared to

〔Effect of the invention〕

As explained above, according to the present invention, semi-insulating properties are ensured for most of the acceptor impurity diffusion region generated in the semi-insulating buried layer of the laser, preventing leakage current and improving characteristics such as dark value current and efficiency. Realize. As a result, it becomes possible to increase output and expand the operating temperature range, contributing to the advancement of optical application systems.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a diagram illustrating the hole concentration distribution, Fig. 3 (al to (dl) is a schematic side sectional view of the process order of the embodiment of the present invention, Fig. 4 is a conventional This is a schematic side sectional view of an example. In the figure, l is an n-type InP substrate, 2 is an n-type rnP confinement layer, 3 is an InGaAsP active layer, 4 is an n-type 1nP confinement layer, 5 is an f-type 1nGaAsP contact layer, 6 is a semi-insulating buried layer, 7s is a high concentration region of acceptor impurity diffusion, 7t is a low concentration tail region of acceptor impurity diffusion, 8 is an n-side electrode, and 9 is an n-side electrode. trouble

Claims (1)

[Scope of Claims] A semiconductor layer that embeds the mesa region of a semiconductor substrate in which a striped mesa region including an active layer and a confinement layer of mutually opposite conductivity types is formed is added to the semiconductor layer from the semiconductor substrate during a manufacturing process. The maximum concentration in the tail of the concentration distribution of acceptor impurities diffusing into Na
When , epitaxial growth is performed such that the concentration Nd of donor impurities that generate conduction electrons and the concentration Nt of acceptor impurities that form deep levels that make the semiconductor layer semi-insulating are as follows: Nt>Nd>Na A method for manufacturing a semiconductor light emitting device.