Vitali Soukhoveev

Diffusion-limited nonradiative recombination at extended defects in hydride vapor phase epitaxy GaN layers

Time-resolved free-carrier absorption and transient grating techniques were applied to determine carrier lifetimes and diffusion coefficients in a set of hydride vapor phase epitaxy GaN layers of various thickness (from 10 to 145 μm). A linear increase in nonradiative carrier lifetime in 80–800 K range found to be in a correlation with decrease of the bipolar carrier diffusion coefficient. This correlation confirmed that recombination rate is governed by carrier diffusive flow to the grain boundaries of columnar defects. A model of diffusion-governed nonradiative lifetime was proposed for fitting the measured lifetime values in the layers of different thickness as well as lifetime dependence on temperature or threading dislocation density.

InN Nano Rods and Epitaxial Layers Grown by HVPE on Sapphire Substrates and GaN, AlGaN, AlN Templates

ABSTRACT This paper contains results on InN growth by Hydride Vapor Phase Epitaxy (HVPE) on various substrates including sapphire, GaN/sapphire, AlGaN/sapphire, and AlN/sapphire templates. The growth processes were carried out at atmospheric pressure in a hot wall reactor in the temperature range from 500 to 650oC. Arrays of nano-crystalline InN rods with various shapes were grown directly on sapphire substrates. Continuous InN layers were grown on GaN/sapphire, AlN/sapphire and AlGaN/sapphire template substrates. X-ray diffraction rocking curves for the (00.2) InN reflection exhibit the full width at half maximum (FWHM) as narrow as 0.075 deg. for the nano-rods and 0.128 deg. for the continuous layers grown on GaN/sapphire templates. INTRODUCTION Group III nitride compounds using InGaN-based active regions have attracted much attention as structures for short wavelength emitters operated in visible spectral range. Ability to grow high-quality thick InN-based active layers thought to be a way for further increasing the light emitters efficiency. Hydride vapor phase epitaxy (HVPE) is well-known method to produce both thick low-defect GaN, AlGaN, AlN templates and free-standing GaN substrates for nitride device fabrication. One of the major technical issues in the development of InN materials is low dissociation temperature and high dissociation pressure of InN. Results of InN and InGaN growth by HVPE are limited. First experiments have been reported more than 25 years ago when InN layers were grown using reaction between ammonia and InCl