Impact of Polarization Charges on Threshold Voltage and Band Offset in AlGaN/GaN Heterostructures

The impact of polarization charges on the band profile and the threshold voltage of two‐dimensional electron gas (2DEG) is studied on AlGaN/GaN and GaN/AlGaN/GaN high electron mobility transistor (HEMT) heterostructures. A model incorporating polarization charges with finite thickness model is used to calculate the threshold voltage of HEMTs ( V th ). On AlGaN/GaN heterostructures, the sheet carrier concentrations ( n s ) obtained using the calculated V th agrees well with experimental results reported in literature. On GaN/AlGaN/GaN heterostructures, Schottky diode samples are prepared and V th obtained by capacitance–voltage characterization agrees with that calculated using proposed model with reasonable material parameters. The proposed model also suggests that the band offset at a heterojunction can be modified by the polarization charges.