M. Amilusik

Preparation of Free-Standing GaN Substrates from Thick GaN Layers Crystallized by Hydride Vapor Phase Epitaxy on Ammonothermally Grown GaN Seeds

Crystallization of GaN by hydride vapor phase epitaxy (HVPE) on ammonothermally grown GaN seed crystals is described. The initial growth conditions for HVPE are determined and applied for further bulk growth. Smooth GaN layers up to 1.1 mm thick and of excellent crystalline quality, without cracks, and with low dislocation density are obtained. Preparation of the free-standing HVPE-GaN crystal by slicing and structural and optical quality of the resulting wafer are presented.

Preparation of free-standing GaN substrates from GaN layers crystallized by hydride vapor phase epitaxy on ammonothermal GaN seeds

Crystallization of GaN by hydride vapor phase epitaxy (HVPE) on ammonothermally grown GaN seed crystals is overviewed. Morphology of the crystal growing surface at the beginning of the crystallization process and at the end of it is presented. Based on these results a rough growth model is proposed. Smooth GaN layers up to 1 mm thick and of a high purity, excellent crystalline quality, without any cracks, and with a low dislocation density are grown. Preparation of the free-standing HVPE-GaN crystals by slicing as well as structural, electrical and optical qualities of the resulting wafers are reported and discussed.

HVPE-GaN growth on ammonothermal GaN crystals

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.

Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds

GaN crystals were grown by hydride vapor phase epitaxy (HVPE) and doped with C. The seeds were high-structural-quality ammonothermally crystallized GaN. The grown crystals were highly resistive at 296 K and of high structural quality. High-temperature Hall effect measurements revealed p-type conductivity and a deep acceptor level in the material with an activation energy of 1 eV. This is in good agreement with density functional theory calculations based on hybrid functionals as presented by the Van de Walle group. They obtained an ionization energy of 0.9 eV when C was substituted for N in GaN and acted as a deep acceptor.

Role and influence of impurities on GaN crystal grown from liquid solution under high nitrogen pressure in multi-feed-seed configuration

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.

Homoepitaxial HVPE GaN growth on non- and semi-polar seeds

In this article homoepitaxial HVPE-GaN growth in directions other than [0001] 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: N2, H2, and a 50% mixture of N2 and H2. 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.

Crystallization of HVPE-GaN:Mn with metallic Mn as dopant source (Conference Presentation)

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.

HVPE-GaN growth on GaN-based advanced substrates by Smart CutTM

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 CutTM 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.