Recent advances in GaN transistors for future emerging applications

Abstract

In this paper, recent advances in GaN‐based transistors for power switching and millimeter wave communications are reviewed. These two applications are emerging in addition to the widely developed power amplifiers at microwave frequencies mainly for cellular base stations. Reduction of the fabrication cost is strongly required for power switching GaN transistors, which is enabled by our epitaxial growth technology on large area Si substrates. Another requisite for the application is to achieve normally‐off operation and our novel device structure called Gate Injection Transistors (GIT) enables it with low enough specific on‐resistance (Ron · A) and high drain current. Here, we also present the world highest breakdown voltage of 10400 V in AlGaN/GaN HFETs, extracting full advantage of the high breakdown strength of GaN. The used poly AlN passivation works as a surface heat spreader with its high thermal conductivity, which effectively relieves the channel temperature resulting in lower thermal resistances. The GaN device for future millimeter wave communication consists of MIS‐type gate using so‐called “in‐situ” deposited SiN as a gate insulator, which exhibits high fmax of 203 GHz and low noise figure of 1.4 dB at 28 GHz. The presented GaN transistors are promising for the two future emerging applications demonstrating high enough potential of the material systems. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterisation of the effect of surface passivation with SiO2/SiN on deep levels in AlGaN/GaN/Si HEMTs

“…This includes the unique capabilities of achieving high breakdown voltage, high current density, high cutoff frequencies, highly linear characteristics, and high operating temperatures [1,2]. Recently, impressive device performances in AlGaN/GaN HEMTs have been reported such as high output power of 40 W/mm at 4 GHz [4], current gain cut-off frequency of 370 GHz breakdown voltage of 10400 V [5]. An understanding of defects localized in structures is essential for improving the quality and performance of devices.…”

Atomic layer deposited HfO2 based metal insulator semiconductor GaN ultraviolet photodetectors

“…AlGaN/GaN based HEMTs is particularly attractive for nextgeneration RF/microwave power amplifiers due to its excellent performances in high temperature and high power operations at microwave frequencies [4]. Until now HEMTs, operating at high power densities and at frequencies up to several giga hertz have been reported [5]. Owing to small size, high performance and low cost characteristics of GaN based UV PDs, It is an appropriate candidate for various applications such as flame detection, missile warning and space monitoring [6e8].…”

Investigation of deep levels in bulk GaN

“…Using this approach, crystalline material of high quality and low threading dislocation (5×10 4 cm -2 ) was produced. Moving on to the question of pdoped GaN, the first p-type GaN with a hole concentration of ~2×10 16 cm -3 was fabricated in 1989 by Amano et al [40] in which magnesium (Mg) was used as the dopant. They discovered that Mg was forming a complex with H during cooling after growth and in order to activate the Mg as p-dopant the GaN has to be annealed in a hydrogen-free atmosphere or irradiated by electrons.…”