Improved dc characteristics of AlGaN/GaN high-electron-mobility transistors on AlN/sapphire templates

Abstract

High-electron-mobility transistors (HEMTs) have been demonstrated on both AlN/sapphire templates and sapphire substrates, and the dc characteristics of the fabricated devices were examined at room temperature. Better dc characteristics with high extrinsic transconductances and drain current densities were observed in the HEMTs grown on AlN/sapphire templates when compared with the HEMTs on sapphire substrates. Extrinsic transconductances of 214 and 137 mS/mm for Wg/Lg=15/2 μm HEMTs on AlN/sapphire templates and HEMTs on sapphire substrates were achieved, respectively. The enhancement of dc characteristics with small variations in threshold voltage (⩽130 mV) is due to the reduction of dislocation density (1.5×108 cm−2). The decrease of dark spot density has been confirmed in the GaN grown on AlN/sapphire templates using cathodoluminescence measurements. The advantage of using AlN/sapphire templates is that low dislocation density GaN layers at a high temperature can be grown without using low-temperature-grown GaN buffer layers.

MOCVD growth and electrical studies of p-type AlGaN with Al fraction 0.35

“…The advantages of using an AlN epitaxial layer as a template for defect density reduction of the subsequent AlGaN layers have been demonstrated in several previous experiments [15,16]. After optimization, X-ray symmetric diffraction (0 0 0 2) revealed narrow full width at half maximum (FWHM) for both rocking and o À 2y scan peaks: 323 arc s for rocking scan and 298 arc s for o À 2y scan, respectively.…”

Trap states in n‐GaN grown on AlN/sapphire template by MOVPE

“…On the other hand, it was reported that high crystalline quality epitaxial AlN films grown on sapphire substrate at high temperature are promising template for GaN epitaxial growth [1]. The superior performance of GaNbased devices, high electron mobility transistor (HEMTs), grown on epitaxial AlN/sapphire template has also been shown [2][3][4]. Besides, an understanding of defects in these materials is essential for improving material quality and device performance.…”

An Unexpected Photoelectronic Effect from [Co(en)3]2(Zr2F12)(SiF6)⋅4 H2O, a Compound Containing an H‐Bonded Assembly of Discrete [Co(en)3]3+, (Zr2F12)4−, and (SiF6)2− Ions

“…[1][2][3][4][5] In recent decades, much effort has been directed toward the synthesis of pnictide-and chalcogenide-based inorganic semiconductor materials such as GaN, [6] SiC, [7] ZnO 2 , [8] and SnO 2 [9] because of their comparatively wide HOMO-LUMO gaps. There has been little investigation, however, of the photoelectronic properties of molecular solids.…”