The influence of threading dislocation density on Hall effects in free-standing GaN substrates

Free-standing GaN substrates are of great importance for short wavelength Laser Diodes (LDs) and high performance Light Emitting Diodes (LEDs) applications. One of the technical barriers for the applications is relatively high threading dislocation density (TDD) in GaN substrates known as non-radiative centers. In this paper, we analyzed the influence of TDD to Hall effects in Si-doped GaN free-standing substrates grown by Hydride Vapor Phase Epitaxy(HVPE). To verify the role of threading dislocations as deep acceptor level and carrier scattering lines, we compared active carrier concentration and Si doping concentration[nSi] of each GaN substrate with different DD. In addition, we measured O doping concentration[nO] of unintentionally doped(UID) GaN substrate that had similar DD with the Si-doped GaN substrate to consider the influence of doped O known as main background impurity, and compared the Hall characteristics of UID GaN with that of the Si-doped GaN. From the results, it was experimentally postulated that threading dislocations function as trap centers disturbing the movement of n-carriers in GaN substrates. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)