The main objective of this paper is crystallization of AlGaN by HVPE method. Source of Al will be metallic aluminum. Hydrochloride flow will be set above the Al source at temperature of 500ºC and as a result of reaction AlCl will form. Aluminum monochloride will be transported to the growth zone of AlGaN. The following growth parameters will be established and analyzed: i/ growth temperature, ii/ flows of gas reagents (HCl above gallium, HCl above metallic Al, ammonia), iii/ carrier gas composition (N2 or nonreactive gas). Determining proper parameters should result in a stable growth of HVPE-AlGaN layers with a desired composition of aluminum (Al content from 1 to 25%). Distribution of aluminum will be uniform in the grown layers. HVPE-AlGaN will be thick up to 100 µm. Their diameter will depend on the used seed – up to 2-inch. Structural, optical and electrical properties of HVPE-AlGaN will be examined and presented in this paper.
The main objective of this paper is crystallization of semi-insulating material with resistivity ~109 Ωcm in temperature range between 296 K and 1000 K. No free carriers should be activated at elevated temperature. Source of Mn dopant will be metallic manganese. Hydrochloride flow will be set above the Mn source and as a result of reaction MnCl2 will form. Manganese dichloride will be transported to the growth zone of GaN. The following growth parameters will be established and analyzed: i/ growth temperature, ii/ flows of gas reagents (HCl above gallium, HCl above metallic Mn, ammonia), iii/ carrier gas composition (N2, H2, mixture of N2 + H2, or nonreactive gas), iv/ temperature of metallic Mn source. Determining proper parameters should result in a stable growth of HVPE-GaN:Mn crystals with a desired morphology (hillocks). Distribution of manganese dopant will be uniform in the grown layer. HVPE-GaN:Mn will be thicker than 1 mm. Their diameter will depend on the used seed – up to 2-inch. The layers will be removed from the seeds by slicing procedure and as a result free-standing HVPE-GaN:Mn will be obtained. Structural, optical and electrical properties of this material will be examined and presented.
Advanced Substrates consist of a 200-nm-thick GaN layer bonded to a handler wafer. The thin layer is separated from source material by Smart Cut<sup>TM</sup> technology. GaN on Sapphire Advanced Substrates were used as seeds in HVPE-GaN growth. Unintentionally doped and silicon-doped GaN layers were crystallized. Free-standing HVPE-GaN was characterized by X-ray diffraction, defect selective etching, photo-etching, Hall method, Raman spectroscopy, and secondary ion mass spectrometry. The results were compared to HVPE-GaN grown on standard MOCVD-GaN/sapphire templates.
In this article homoepitaxial HVPE-GaN growth in directions other than  is described. Three crystallization runs on (11-20), (10-10), (20-21), and (20-2-1) seeds were performed. In each experiment a different carrier gas was used: N<sub>2</sub>, H<sub>2</sub>, and a 50% mixture of N<sub>2</sub> and H<sub>2</sub>. Other conditions remained constant. An influence of the growth direction and carrier gas on growth rate and properties (morphology, structural quality, and free carrier concentration determined by Raman spectroscopy) of obtained crystals was investigated and discussed in details. For all crystallographic directions a lower growth rate was determined with hydrogen used as the carrier gas. Also, the highest level of dopants was observed for crystals grown under hydrogen. A possibility to obtain highly conductive GaN layers of high quality without an intentional doping is demonstrated.
Role and influence of impurities like: oxygen, indium and magnesium, on GaN crystals grown from liquid solution under high nitrogen pressure in multi-feed-seed configuration is shown. The properties of differently doped GaN crystals are presented. The crystallization method and the technology based on it (for obtaining high quality GaN substrates) are described in details. Some electronic and optoelectronic devices built on those GaN substrates are demonstrated.
HVPE crystallization on ammonothermaly grown GaN crystals (A-GaN) is described. Preparation of the (0001) surface of the A-GaN crystals to the epi-ready state is presented. The HVPE initial growth conditions are determined and demonstrated. An influence of a thickness and a free carrier concentration in the initial substrate on quality and mode of growth by the HVPE is examined. Smooth GaN layers of excellent crystalline quality, without cracks, and with low dislocation density are obtained.