Electrical Investigation of Turn-On Capacitance Recovery Characteristics in Carbon-Doped AlGaN/GaN Hetero-Structures Grown on Si Substrates

Abstract

We have investigated a detailed relation between turn-on capacitance recovery characteristics and deep-level defects in AlGaN/GaN hetero-structures with heavily carbon-doped GaN (GaN:C) buffer layers grown on Si substrates in order to understand bulk-related current collapse phenomena. With increasing the carbon doping concentration of the GaN:C buffer layer from ∼1 × 1017 up to ∼1 × 1019 cm−3, turn-on capacitance recovery time after off-bias stress becomes extremely long in the dark and two deep-level defects with their optical onset at ∼2.75 and ∼3.25 eV below the conduction band are significantly enhanced. These carbon-related defects in the semi-insulating GaN:C buffer layer probably behave as acceptor-like trapping centers and are negatively charged up even in the depletion regions under the off-bias state. Consequently, under the sequential turn-on state, charge neutralization of these specific defects is considered to advance very slowly via a hole capture process, which is strongly responsible for the turn-on capacitance recovery characteristics.