Abstract
The current state of dopant assessment for the optimization of the III-nitride-based heterostructures for high frequency, high power, and light emission applications relies heavily on quantitative chemical analysis techniques. In such complex heterostructures, determination of p-type carrier density of the cap layer, control of background concentration, and assessment of polarization induced confined carriers are necessary for the realization of optimal devices. None of these can be completely inferred from chemical analysis owing to several material and growth issues including poor activation of Mg, presence of O impurities, and amphoteric nature of carbon impurities. Here, as regions of interest require nanometer resolution, especially near the interfaces featuring triangular quantum wells and exhibiting electron/hole confinement, exploitation of the behavior of the nanosize metal–semiconductor junction formed between the metallic scanning probe microscopy probe and the III-nitride surface is promising for carrier determination. By combining two techniques sensitive to local change in capacitance and rectifying characteristic of conduction at the nanoscale, the nature of free carriers originating from extrinsic n-type and p-type dopants and polarization induced confined carriers, two-dimensional electron gas and hole gas, were eventually revealed across III-nitride heterostructures.
Highlights
N III-N device technology is facing doping and material characterization issues
As regions of interest require nanometer resolution, especially near the interfaces featuring triangular quantum wells and exhibiting electron/hole confinement, exploitation of the behavior of the nanosize metal–semiconductor junction formed between the metallic scanning probe microscopy probe and the III-nitride surface is promising for carrier determination
The high p-type doping of the GaN cap layer required for bringing the high electron mobility transistors (HEMTs) in the normally OFF mode[2] is hindered by a poor activation of Mg dopants in the metal-organic chemical vapor deposition reactors.[3,4]
Summary
N III-N device technology is facing doping and material characterization issues. For example, the high p-type doping of the GaN cap layer required for bringing the high electron mobility transistors (HEMTs) in the normally OFF mode[2] is hindered by a poor activation of Mg dopants in the metal-organic chemical vapor deposition reactors.[3,4]. Even though in the calculation the hole densities at interfaces 1 and 2 of the transition layers is almost 10Â that of the GaN buffer/AlGaN interface, in the electrical measurements, which will be discussed later, the two interfaces show diminished conductivity and SCM signal indicative of the low carrier density.
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