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We report on the influence of deep pits on three terminal-off breakdown of AlGaN/GaN high electron mobility transistors (HEMTs) grown on 4-in. silicon by metalorganic chemical vapor deposition (MOCVD). For devices with deep pits, the breakdown was greatly affected by excess leakage through buffer and substrate. The reason for excess leakage was established using transmission electron microscope (TEM) image. The TEM image reveals that deep pits originate from silicon substrate because of Ga etching Si substrate at high growth temperatures. These etch pits and their surface termination in the form of hexagonal pyramid pits act like micro-pipes causing high leakage through the substrate and buffer. The three terminal-off breakdown of the HEMTs decreased rapidly as the density of deep pits increase.

Influence of thickness and growth condition of AlN spacer on electrical properties of AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) grown on 4-in. Si substrate was studied. Hall measurements show the mobility of AlGaN/AlN/GaN heterostructure varies with different thickness of AlN spacer and a narrow high-mobility window was obtained. The surface and structure studies indicate that both increasing growth temperature and lowering pressure benefit the quality of AlN and AlGaN, which leads to improvement of Hall mobility, except the temperature higher than that of GaN growth. Drain current-voltage (I ds -V ds ) characteristics of such HEMTs exhibit the maximum current density (I max ) and tranconductance (g max ) have the similar trend with the mobility due to different interface roughness and piezoelectric field induced by part relaxation of tensile strain in AlGaN grown on AlN. The optimum properties of HEMT (I max ¼ 807 mA/mm, g max ¼ 221 mS/mm) are obtained when 1 nm AlN spacer grown at 1130 C and 100 Torr.

This paper reports enhanced internal-quantum-efficiency (IQE) in InGaN-based multi-quantum-well (MQW) grown on Si(111) substrate with underlying strained-layer-superlattice (SLS) cladding layer for application in LDs and LEDs. In comparative study between a thick Al0.03Ga0.97N bulk and an Al0.06Ga0.94N/GaN SLS cladding layer, transmission-electron-microscopy (TEM) images reveal that Al0.06Ga0.94N/GaN SLS cladding layer is effective to suppress threading dislocations. A higher IQE has been achieved in sample with underlying Al0.06Ga0.94N/GaN SLS cladding layer, compared to that of Al0.03Ga0.97N bulk cladding layer. IQE of 31.6% has been achieved in sample with underlying Al0.06Ga0.94N/GaN SLS cladding layer when the MQW thickness is reduced to 2 nm.

We report growth pits, structural, electrical, and optical data for AlGaN/GaN HEMT samples grown on 4″ silicon substrates. The samples in this study were all grown on 4″ p‐Si (111) substrate by metalorganic chemical vapor deposition (MOCVD). Optical microscopy, Hall‐effect measurements, photoluminescence, high resolution X‐ray Diffraction (HRXRD) were performed to investigate the morphological, electrical and optical properties and crystal quality of the samples. According to these data, the relationship between the growth pits, optical and structural properties were studied (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)