Impedance Elements of Significant Junctions in InGaN Light-Emitting Diodes Studied by Electric Modulus Spectroscopy

The investigation of the heterojunction properties in InGaN-based light-emitting diodes (LEDs) is important to the development of LEDs, because charge carrier transport in the LED is governed by the junctions. In this paper, it is proven that the impedance properties of the significant junctions in InGaN/GaN multiple quantum well (MQW) LEDs can be characterized by electric modulus (M) spectroscopy. An equivalent circuit is given to represent the significant junctions of the LEDs. The bias and temperature dependence of impedance parameters of the main active junction and the p-type AlGaN/GaN junctions were studied by {M} spectroscopy. The existence of the AlGaN/GaN junction degrades the efficiency in ac signal transmission and causes a transition in the effective capacitance of the device.