Effect of carbon doping on buffer leakage in AlGaN/GaN high electron mobility transistors

Abstract

Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N-and Gaface AlGaN/GaN heterostructures

Electric Field Reduction in C-Doped AlGaN/GaN on Si High Electron Mobility Transistors

“…RF devices frequently make use of iron (Fe) doping to render the GaN insulating, but for the higher voltages required for many power switching applications, it has been found that carbon (C) doping delivers higher breakdown voltage and lower off-state leakage [1,2]. Unfortunately it has also been found that using carbon can result in a transitory increase in R ON , also known as current-collapse (CC), when switched from the off to the on-state [2,3]. With field plates now universally used to control surface effects, it is clear that the remaining CC in these devices mostly results from charge storage in deep levels in the buffer.…”

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.…”

Impact of substrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN grown by molecular beam epitaxy

“…2 Along with the desired SI behavior, however, carbon impurity incorporation may also have inadvertent and potentially deleterious impact on device performance. To emphasize SI behavior via carbon doping while minimizing undesired effects, the overall impact of carbon-related impurity states and, in particular, the precise mechanism for SI behavior in MBE-grown GaN: C must be understood as a function of growth conditions and doping levels.…”

“…One series of samples ͑HT͒ was grown at T s = 720°C, which is typical for high performance AlGaN/ GaN HFET devices grown by MBE. 2 Diode structure consisted of unintentionally doped GaN of 700 Å thickness grown on a Lumilog two-step lateral epitaxial overgrowth template, followed by a 3800 Å n + -GaN: Si lateral conduction layer, upon which was grown a 6200 Å GaN:C:Si layer. Mesas were formed by reactive ion etching, and a semitransparent Ni layer and a Ti/ Ni/ Al/ Au stack formed the Schottky and ohmic contacts, respectively.…”