The electrical effects of SiNx deposition on GaN
MESFETs have been investigated. Significant effects induced from the
dielectric coating have been observed depending on the deposition
temperature used in the technological process. A power density increase
of 30% has been observed after the device passivation performed at
[Show abstract][Hide abstract] ABSTRACT: A surface leakage test structure is used to isolate the surface and bulk leakage currents in AlGaN/GaN based devices. Passivation of post-processed devices with stoichiometric Si3N4 resulted in reduced surface leakage, which suggests that surface passivation acts to suppress the AlGaN surface conduction, possibly through a reduction in surface states. However, passivation with low temperature grown SiNx, which has a high density of interfacial states increased the surface leakage component instead. This implies that surface conduction is critically dependent on the amount of surface states present. The surface leakage component is also found to be thermally activated with an activation energy of 0.19 eV. When the devices are driven to hard breakdown, a sharp rise in the surface current is typically observed, which strongly suggests that breakdown in these devices is dominated by surface edge effects.
[Show abstract][Hide abstract] ABSTRACT: An overview is presented of progress in GaN electronic devices along with recent results from work at UCSB. From 1995 to 2001, the power performance of AlGaN/GaN high electron mobility transistors (HEMT) improved from 1.1 to 11 W mm −1 , respectively. The disadvantage of the low thermal conductivity of the sapphire substrate was mitigated by flip-chip bonding onto AlN substrates, yielding large periphery devices with an output power of 7.6 W. A variety of HEMT amplifier circuits have been demonstrated. The first AlGaN/GaN heterojunction bipolar transistor (HBT) was demonstrated in 1998, with a current gain of about 3. By developing the technique of emitter regrowth, a current gain of 10 was achieved in both GaN BJTs and AlGaN/GaN HBTs. A common emitter current gain cutoff frequency of 2 GHz was measured. Critical issues involved in the growth of high quality AlGaN/(AlN)/GaN heterostructures and GaN:Mg by metal–organic chemical vapour deposition (MOCVD) and molecular beam epitaxy (MBE) and the device fabrication are discussed.
[Show abstract][Hide abstract] ABSTRACT: We present an experimental analysis on the effect of dielectric stress on the electrical characteristics of AlGaN/GaN HFETs. Issues such as maximum current (I<sub>d-max</sub>), gate leakage and current collapse are presented. Different dielectric deposition conditions were used to vary the amount of stress induced on the wafer and the devices were measured before and after passivation. A striking feature observed was the strong dependence of I<sub>d-max</sub> on the amount of stress induced by the dielectric. I<sub>d-max</sub> increases when the stress is tensile and reduces when it is compressive. The rise in leakage current was found to be dependent on the dielectric film itself and not on the stress induced, which suggests that a surface effect is responsible for the leakage mechanism.
Electron Devices for Microwave and Optoelectronic Applications, 2002. EDMO 2002. The 10th IEEE International Symposium on; 12/2002
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