Chemical etchant dependence of surface structure and morphology on GaN(0001) substrates

Abstract: We studied the procedure of cleaning GaN(0001) substrate surfaces by wet etching and subsequent annealing in ultrahigh vacuum for two different types of freestanding GaN wafers: hydride vapor phase epitaxy (HVPE) crystal and Na flux liquid phase epitaxy (LPE) crystal wafers. A flat surface containing GaN(0001)2×2 reconstruction was successfully achieved on both HVPE and LPE surfaces by etching in HF and subsequent annealing at ∼550°C but was not achieved by etching in HCl, NaOH, and HNO3. [Copyright &y& Elsevier]