Estimation of background carrier concentration in fully depleted GaN films

TL;DR

This paper introduces a simple model to accurately estimate background carrier concentrations in fully depleted GaN films using capacitance-voltage measurements, validated by experimental data.

Contribution

The paper presents a novel, effective model for extracting carrier concentrations in fully depleted GaN films from C-V measurements, overcoming limitations of conventional techniques.

Findings

Model accurately predicts carrier concentrations in fully depleted GaN.

Validation shows excellent agreement with Hall measurements.

Technique can be extended to other semiconductor structures.

Abstract

Buffer leakage is an important parasitic loss mechanism in AlGaN/GaN HEMTs and hence various methods are employed to grow semi-insulating buffer layers. Quantification of carrier concentration in such buffers using conventional capacitance based profiling techniques is challenging due to their fully depleted nature even at zero bias voltages. We provide a simple and effective model to extract carrier concentrations in fully depleted GaN films using capacitance-voltage (C-V) measurements. Extensive mercury probe C-V profiling has been performed on GaN films of differing thicknesses and doping levels in order to validate this model. Carrier concentrations as extracted from both the conventional C-V technique for partially depleted films having the same doping concentration, and Hall measurements show excellent agreement with those predicted by the proposed model thus establishing the utility of this technique. This model can be readily extended to estimate background carrier concentrations from the depletion region capacitances of HEMT structures and fully depleted films of any class of semiconductor materials.