Dislocation analysis in p-type 4H-SiC: Etching morphologies and electronic properties

Abstract

As the foundational material for high-voltage n-channel Insulated Gate Bipolar Transistors (IGBTs), p-type 4H silicon carbide (4H-SiC) substrates lack comprehensive analysis of dislocations. This study extensively examines the dislocations in p-type 4H-SiC crystals grown by Physical Vapor Transport (PVT) and Top-Seeded Solution Growth (TSSG) methods using molten alkali etching technology. Optimal process parameters for etching p-type 4H-SiC wafers were identified, and different types of dislocations—threading edge dislocations (TEDs), threading screw dislocations (TSDs), and basal plane dislocations (BPDs)—were distinguished. Finally, the electronic properties of TEDs and BPDs were determined using Kelvin probe force microscopy. The study found that doping with dominant impurity Al converts deep-level TED and BPD into shallow acceptor states. This implies that Al impurities tend to occupy sites at TED and BPD dislocations, forming TED-Al4 and BPD-Al2 composite dislocations with shallow acceptor characteristics. This work not only provides guidance for molten alkali etching of p-type 4H-SiC but also enhances our understanding of the electronic behaviors of dislocations in p-type 4H-SiC.