Optical semiconductor device and manufacturing method therefor

Abstract

To provide an elemental technique for improving the emission intensity of deep ultraviolet light from a light emitting layer made of an AlGaInN-based material, in particular, an AlGaN-based material. First, an AlN layer is grown on a sapphire surface. The AlN layer is grown under a NH3-rich condition. The TMAl pulsed supply sequence includes growing an AlGaN layer for 10 seconds, interrupting the growth for 5 seconds to remove NH3, and then introducing TMAl at a flow rate of 1 sccm for 5 seconds. After that, the growth is interrupted again for 5 seconds. Defining this sequence as one growth cycle, five growth cycles are carried out. By such growth, an AlGaN layer having a polarity of richness in Al can be obtained. The above sequence is described only for illustrative purposes, and various variations are possible. In general, the Al polarity can be achieved by a process of repeating both growth interruption and supply of an Al source.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical semiconductor device and a manufacturing method therefor. In particular, it relates to a technology of a deep ultraviolet light emitting device using a group III-V compound semiconductor.[0003]2. Background Art[0004]In recent years, in technical fields of semiconductor light emitting devices using PN junction, such as light emitting diodes and laser diodes, nitride semiconductors containing nitrogen as a group-V element have been drawing lots of attention, and research and development thereof have been actively carried out. Nitride semiconductors, such as AlN, GaN and InN, are direct transition semiconductors. Furthermore, a ternary or quaternary mixed crystal is capable of emitting light from infrared rays to deep ultraviolet rays by changing the band gap by appropriately determining the composition.[0005]Furthermore, a semiconductor light emitting device that has a light emi...

AI Technical Summary

Benefits of technology

[0007]An object of the present invention is to provide an elemental technique for improving the emission intensity of deep ultraviolet light from a light emitting layer made of an AlGaInN-based material, in particular, an AlGaN-based material.

[0016]According to the present invention, a high-quality AlGaN buffer for an ultraviolet LED can be produced. The pulsed supply of TMAl enables the group III polarity to be achieved. The pulsed supply of TMAl advantageously reduces the threading dislocation.

[0017]Using a template formed of the high-quality AlGaN buffer layer formed by pulsed supply of TMAl substantially improves the maximum power of the ultraviolet LED, compared with the prior art.

Problems solved by technology

However, in manufacturing a semiconductor light emitting device using a nitride semiconductor, it is required to use a sapphire substrate, for example, as an epitaxial growth substrate, because it is difficult, or expensive even if possible, to produce a high-quality and large-area epitaxial growth substrate of a nitride semiconductor. FIG. 14 shows a relationship between the lattice constant and the band gap energy (corresponding to the wavelength) of an InAlGaAs-based quaternary mixed crystal.

As a result, there is a problem that the threading dislocation density of the nitride semiconductor thin film increases because the lattice constant mismatch increases.

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