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We report nano-selective area growth (NSAG) of BGaN by MOCVD on AlN/Si(111) and GaN templates resulting in 150 nm single crystalline nanopyramids. This is in contrast to unmasked or micro-selective area growth, which results in a multi-crystalline structure on both substrates. Various characterization techniques were used to evaluate NSAG as a viable technique to improve BGaN material quality on AlN/Si(111) using results of GaN NSAG and unmasked BGaN growth for comparison. Evaluation of BGaN nanopyramid quality, shape and size uniformity revealed that the growth mechanism is the same on both the templates. Further STEM analysis of BGaN nanopyramids on AlN/Si (111) templates confirmed that these are single-crystalline structures without any dislocations, likely due to single nucleation occurring in the 80 nm mask opening. CL results correspond to boron content between 1.7% and 2.0% in the nanopyramids. We conclude that NSAG is promising for growth of high-quality BGaN nanostructures and complex nano-heterostructures, especially for low-cost silicon substrates. [ABSTRACT FROM AUTHOR]

Planar (In,Ga)N layers were grown on nanostripe arrays composed of InGaN/GaN multi quantum wells (MQWs) by metal–organic chemical vapor deposition. The MQW nanostripe arrays with height to width aspect ratios of about 0.5 and 1 were fabricated from planar coherently strained InGaN/GaN MQW samples. Independent of their aspect ratio, the nanostripes exhibited elastic relaxation perpendicular to the stripe direction after pattern fabrication, resulting in an a⊥ lattice constant perpendicular to the stripe direction larger than that of the GaN base layer. In a subsequent step, (In,Ga)N layers were grown on top of the nanostripe arrays, leading to the formation of planar films with a similar a⊥ lattice constant as the MQW stripes beneath. Bright luminescence was recorded from the planar, partially relaxed re-grown (In,Ga)N layers grown on the stripe arrays with an aspect ratio of 1. Plastic relaxation of the MQW stripes was observed after (In,Ga)N regrowth for samples with a stripe aspect ratio of 0.5, leading to luminescence quenching. [ABSTRACT FROM AUTHOR]

In this paper, we performed a high-resolution measurement of channel temperature rise in GaN-based high electron mobility transistors (HEMTs). Cathodoluminescence spectroscopy in the scanning electron microscope was used to probe the temperature rise with several tens of nanometers spatial resolution and accuracy better than ±8 °C. We also determined the temperature distribution and peak temperature change with the power density in active AlGaN/GaN HEMTs in the source–gate and gate–drain openings. The measured results agree reasonably well with physical 2D electrothermal simulations and Raman thermography. [ABSTRACT FROM AUTHOR]

GaN-on-Si transistors attract increasing interest for power applications. However, the breakdown behavior of such devices remains below theoretical expectations, for which the Si substrate is typically made responsible. In this work, the effect of the thickness of an aluminum nitride buffer layer on the vertical breakdown voltage, measured relative to a grounded silicon substrate, has been investigated. A voltage-polarity-dependent breakdown mechanism has been observed. It has been found that the breakdown in the positive bias voltage regime is initiated by carrier injection, for which the carriers originate from an inversion channel formed between the epitaxial layers and the p-silicon substrate. TCAD simulations have confirmed the proposed explanations, and suggest that appropriate modification of the electronic structure at the AlN/silicon interface could significantly improve the vertical breakdown voltage. [ABSTRACT FROM AUTHOR]