Effect of Polarization Field on the Photocurrent Characteristics of GaN/AlN Multi-Quantum-Well Avalanche Photodiode

TL;DR

This study investigates how polarization fields influence the photocurrent behavior of GaN/AlN multi-quantum-well avalanche photodiodes, revealing their significant role in carrier multiplication and electron transport mechanisms.

Contribution

It provides the first detailed analysis of polarization field effects on photocurrent characteristics in GaN/AlN MAPDs, highlighting mechanisms previously overlooked in simplified models.

Findings

Carrier multiplication driven by interfacial impact ionization influenced by polarization.

Electron tunneling facilitated by polarization field in AlN barriers.

Polarization field impacts electron transport, affecting photocurrent response.

Abstract

Polarization is an important property of GaN/AlN multi-quantum-well (MQW) avalanche diode (MAPD) but has been ignored in recent analyses of MAPD to simplify the Monte Carlo simulation. Here, the photocurrent characteristics of GaN/AlN MAPD are investigated to understand the role of polarization field in the MQW structure. Carrier multiplication in AlN/GaN MAPD is found as a result of interfacial impact ionization not much helped from external field but instead considerably contributed by the polarization field. In addition, the movement of ionized electrons out of quantum well is proved as Fowler-Nordheim tunneling process helped by the polarization field in AlN barrier. Furthermore, the transport of ionized electrons through MQW structure is found influenced by the reverse polarization field in GaN layer, which could be suppressed by the external electric field. With all the three effects, the quick photocurrent increase of GaN/AlN MAPD is ascribed to the efficient transport of interfacial-ionized electrons step by step out of MQW at high voltages, which is in big difference from conventional APD due to avalanche breakdown.