Defect reduction in ZnSe grown by molecular beam epitaxy on GaAs substrates cleaned using atomic hydrogen

Atomic hydrogen is demonstrated to effectively clean GaAs substrates for subsequent growth of ZnSe by molecular beam epitaxy. Optical fluorescence microscopy is shown to be a useful technique to image nonradiative defects related to stacking faults. While the density of stacking faults in ZnSe films grown using conventional thermal cleaning is greater than 107 cm−2, stacking fault densities lower than 104 cm−2 are obtained using atomic hydrogen cleaning. Low-temperature photoluminescence spectra of undoped ZnSe are dominated by excitonic transitions for the low defect density samples in contrast to the high level of defect-related emission from high defect density samples.