Chapter 3 Growth and optical properties of GaN

Abstract

The chapter presents a discussion on the growth and optical properties of galium nitride (GaN). Because GaN has very good thermal and chemical stability, it is an excellent candidate for high-temperature and high-power devices. UV detectors, which can be used in aerospace applications, were fabricated based on GaN wide-bandgap semiconductor. The chapter presents a review and discusses important current results obtained by various workers by studying the photoluminescence properties of GaN and related materials. The experimental techniques covered include optical absorption, photoreflection (PR), modulation spectroscopy, spectroscopic ellipsometry, photoluminescence (PL), time-resolved PL, micro-PL, cathodoluminescence, nonlinear optical techniques such as pump-probe spectroscopy, femtosecond spectrally resolved and time-resolved degenerate four-wave mixing, second harmonic generation, laserinduced gratings, and quantum beats. Important theory papers on band structure and stimulated emission are also presented. GaN exists in two different crystal structures, namely wurtzite and zincblende. GaN can be grown by various methods such as metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), chemical beam epitaxy (GEE), and metal-organic molecular beam epitaxy (MOMBE). For each one of these methods there are different techniques that can be used. Photoluminescence is a very powerful technique to understand the electronic structure and optoelectronic properties of semiconductors. In the luminescence process, the semiconductor in the excited states emits photons and relaxes to the ground state or a lower energy state.