Nitride semiconductor, semiconductor device, and manufacturing methods for the same

Abstract

A nitride semiconductor having a large low-defect region in a surface thereof, and a semiconductor device using the same are provided. Also, a manufacturing method for a nitride semiconductor comprising a layer formation step using a transverse growth technique where surface defects can easily be reduced, and a manufacturing method for a semiconductor device using the same are provided. On a substrate, a seed crystal part is formed in a stripe pattern with a buffer layer in between. Next, crystals are grown from the seed crystal part in two stages of growth conditions to form a nitride semiconductor layer. Low temperature growing parts with a trapezoid shaped cross section are formed at a growth temperature of 1030° C. in the first stage and a transverse growth is dominantly advanced at a growth temperature of 1070° C. to form a high temperature growing part between the low temperature growing parts in the second stage. Thereby, hillocks and conventional lattice defects are reduced in a surface of the nitride semiconductor layer which is above the low temperature growing part.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a nitride semiconductor, for example, which is used for manufacturing a semiconductor laser device or the like, a semiconductor device using the same, and manufacturing methods for the same. [0003] 2. Description of the Related Art [0004] In recent years, III-V group compound semiconductors attract attention as a device material because of their various characteristics. Especially these materials are direct transition type ones and have a band gap width ranging from 1.9 eV to 6.2 eV, so only these materials provide light emitting in a wide region raging from a visible region to an ultraviolet region, and developments thereof as a material of semiconductor light emitting devices such as a semiconductor laser and light emitting diode (LED) are actively progressing. In addition to their wide band gap width, it can be expected that they have high electron saturation velocity and a high b...

AI Technical Summary

Benefits of technology

[0012] The second object of the invention is to provide a manufacturing method for a nitride semiconductor comprising a layer formation step which can easily accomplish few surface defects using a transverse growth technique, and a manufacturing method of a semiconductor device using the above method.

[0016] The nitride semiconductor and the semiconductor device according to the invention comprise the second seed crystal part which has the triangle or trapezoid shaped cross section, and the semiconductor layer which grows based on the second seed crystal part, so the dislocation in crystals is bent on an interface between the second seed crystal part and the semiconductor layer, and this decreases the dislocation penetrating to a surface of the semiconductor layer.

Problems solved by technology

The crystal substrate (or the crystal film) has desirably bulk crystals of a gallium nitride compound, but manufacturing such a kind of bulk crystals is difficult, so the gallium nitride compound is formed by epitaxial growth on a substrate such as sapphire (α-Al2O3), silicon carbide (SiC), or the like in most cases.

However, there is a large difference in lattice mismatching and thermal expansion coefficient between the substrate material such as sapphire or the like and the gallium nitride compound, and lattice defects such as dislocation occur in a layer of the gallium nitride compound to relax distortion thereof.

A lattice defect part serves as a center of non-radiative recombination, which emits no light even if an electron and a hole recombine, or as a leak part of electric currents, which causes damages of characteristics of the semiconductor devices.

However, there is dislocation which passes through an opening part of the growth suppressing layer and penetrates the crystals, and dislocation and defects are increased locally in a region which is above the opening part of the gallium nitride semiconductor layer.

However, also in the method, the dislocation may spread to an upper surface of the seed crystal parts, so the region which is directly over the seed crystal parts becomes a region locally having many dislocation and defects.

Therefore, using these methods is insufficient for reducing the defects of the surface of the gallium nitride semiconductor on a substrate, which is a problem.

Furthermore, the transverse growth in these methods is an incomplete selective growth, and an upward growth also occurs as well as the transverse growth, so that a thickness is rapidly increased during fully performing the transverse growth, and this may result in bowing in a formed gallium nitride semiconductor layer.

Defects may occur in the semiconductor layer being grown on the hillocks and this may damage characteristics of the produced semiconductor device.

In the case of the semiconductor laser, when laser stripes are formed on the hillocks, there are problems of lowering reliability such as laser static characteristics and a life of the laser.

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