Comparative study of buffer designs for high breakdown voltage AlGaNGaN HFETs

Abstract

A comparison of different epilayer concepts to achieve high breakdown voltage AlGaN‐GaN HFETs is presented. A double heterostructure with a low Al‐content Al0.05Ga0.95N back‐barrier as well as a carbon‐doped GaN buffer are investigated with regard to material and device properties. Material analysis reaffirms the incorporation of carbon on a nitrogen lattice site without creation of extended defects or causing memory effects. It is demonstrated that carrier trapping in the buffer using carbon deep acceptors reduces sub‐threshold drain leakage currents in HFET devices enabling breakdown voltages above 1 kV. An undoped GaN channel layer is shown to suppress drain current reduction under pulsed transistor operation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Impact of residual carbon on two-dimensional electron gas properties in AlxGa1−xN/GaN heterostructure

“…[4][5][6] Firstly, the GaN BL has to be semi-insulating (SI) to prevent unwanted current paths underneath the two-dimensional electron gas (2DEG) channel and also to obtain high breakdown voltage with low leakage current. One effective way to achieve this is to introduce acceptor-like impurities, like iron 7 or carbon, [8][9][10] during growth of the GaN BL; however, iron doping has a memory effect rendering doping profile difficult to control. Secondly, in order to alleviate the trapping effect that causes failure of device characteristics, known as current collapse, the level of acceptor-like impurities in the vicinity of 2DEG channel should be minimized.…”

“…13,14 Growth pressure appears to be a more effective way to swing the incorporation of carbon. 9,10 However, one can expect that, as the growth pressure is varied, many other growth parameters are correspondingly changed at the same time, like wafer temperature, deposition profile, and effective V/III ratio. This renders it difficult in establishing a good process for growth of high-uniformity epi-layers on large wafer area.…”

Effect of Carbon Doping and Crystalline Quality on the Vertical Breakdown Characteristics of GaN Layers Grown on 200-mm Silicon Substrates

“…It is clearly seen from this figure that the carbon level decreased with increasing growth pressure and temperature, respectively, in accordance with previously reported results. [12][13][14][15] However, it can be seen that, in our growth system, the response of the carbon level to a change in temperature is more evident than for a change in pressure. In group B, the carbon concentration of layer II in sample B3 was more than 10 times less than that for sample B1 with a growth temperature increased by 50°C.…”

“…[11][12][13] In the literature, growth of highly resistive GaN buffers by auto carbon doping during the metalorganic chemical vapor deposition (MOCVD) growth process has been reported, where the carbon impurities originate from the metalorganic precursors. [13][14][15] The carbon concentration in GaN layers can be controlled through growth parameters such as temperature, pressure, and V/III ratio. [12][13][14][15] However, the effect of these growth parameters on the breakdown voltage characteristics of carbon-doped GaN buffers grown on 200-mmdiameter Si substrates as well as the uniformity aspects have not been reported in previous studies.…”

“…[13][14][15] The carbon concentration in GaN layers can be controlled through growth parameters such as temperature, pressure, and V/III ratio. [12][13][14][15] However, the effect of these growth parameters on the breakdown voltage characteristics of carbon-doped GaN buffers grown on 200-mmdiameter Si substrates as well as the uniformity aspects have not been reported in previous studies.…”