The GaN samples grown for this dissertation were studied by various techniques to characterize their structural, optical, and electrical properties.

This book discusses the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production.

Semiconductors are at the heart of modern living. Almost everything we do, be it work, travel, communication, or entertainment, all depend on some feature of semiconductor technology. Comprehensive Semiconductor Science and Technology, Six Volume Set captures the breadth of this important field, and presents it in a single source to the large audience who study, make, and exploit semiconductors. Previous attempts at this achievement have been abbreviated, and have omitted important topics. Written and Edited by a truly international team of experts, this work delivers an objective yet cohesive global review of the semiconductor world. The work is divided into three sections. The first section is concerned with the fundamental physics of semiconductors, showing how the electronic features and the lattice dynamics change drastically when systems vary from bulk to a low-dimensional structure and further to a nanometer size. Throughout this section there is an emphasis on the full understanding of the underlying physics. The second section deals largely with the transformation of the conceptual framework of solid state physics into devices and systems which require the growth of extremely high purity, nearly defect-free bulk and epitaxial materials. The last section is devoted to exploitation of the knowledge described in the previous sections to highlight the spectrum of devices we see all around us. Provides a comprehensive global picture of the semiconductor world Each of the work's three sections presents a complete description of one aspect of the whole Written and Edited by a truly international team of experts

Gallium nitride is an important material for the production of next-generation visible and near-UV optical devices, as well as for high temperature electronic amplifiers and circuits; however there has been no bulk method for the production of GaN substrates for device layer growth. Instead, thick GaN layers are heteroepitaxially deposited onto non-native substrates (usually sapphire) by one of two vapor phase epitaxy (VPE) techniques: MOVPE (metalorganic VPE) or HVPE (hydride VPE). Each method has its strengths and weaknesses: MOVPE has precise growth rate and layer thickness control but it is slow and expensive; HVPE is a low-cost method for high rate deposition of thick GaN, but it lacks the precise control and heterojunction layer growth required for device structures. Because of the large (14%) lattice mismatch, GaN grown on sapphire requires the prior deposition of a low temperature MOVPE nucleation layer using a second growth process in a separate deposition system. Here we present a novel hybrid VPE system incorporating elements of both techniques, allowing MOVPE and HVPE in a single growth run. In this way, a thick GaN layer can be produced directly on sapphire. GaN growth commences as small (50-100 nm diameter) coherent strained 3-dimensional islands which coalesce into a continuous film, after which 2-dimensional layer growth commences. The coalescence of islands imparts significant stress into the growing film, which increases with the film thickness until catastrophic breakage occurs, in-situ. Additionally, the mismatch in thermal expansion rates induces compressive stress upon cooling from the growth temperature of 1025°C. We demonstrate a growth technique that mitigates these stresses, by using a 2-step growth sequence: an initial high growth rate step resulting in a pitted but relaxed film, followed by a low growth rate smoothing layer. As a result, thick (> 50 [Mu]m) and freestanding films have been grown successfully. X-ray rocking curve linewidth of 105 arcseconds and 10K PL indicating no "yellow" emission indicate that the material quality is higher than that produced by conventional MOVPE. By further modifying the hybrid system to include a metallic Mn source, it is possible to grow a doped semi-insulating GaN template for use in high frequency electronics devices.