Method for noncontact measurement of 2DEG mobility and carrier density in AlGaN/GaN on semi-insulating wafers

Abstract

We present a charge-assisted sheet resistance technique for noncontact wafer level determination of two-dimensional electron gas (2DEG) mobility versus sheet carrier density without any test structures or gates. Instead, the electrical biasing of the 2DEG is provided by surface charge deposition, using a corona charging method. Analysis of the sheet resistance versus deposited charge identifies the 2DEG full depletion condition and enables calculation of the 2DEG sheet carrier density required for the mobility. Results for AlGaN/GaN heterostructures on semi-insulating SiC and sapphire substrates show good agreement with Hall results at a zero-bias condition.