A review of GaN-based optoelectronic devices on silicon substrate

Probing defect states in polycrystalline GaN grown on Si(111) by sub-bandgap laser-excited scanning tunneling spectroscopy

“…The GaN layers were deposited by molecular beam epitaxy under nitrogen-rich conditions (N 2 :Ga beam equivalent pressure ratio of 160) at 720 C. The low temperature, nitrogen rich growth conditions were chosen to avoid the detrimental meltback etching that is known to occur at higher temperatures and Ga-rich conditions. 7 The GaN layers can be expected to exhibit n-type conductivity due to unintentional doping.…”

“…These fluctuations may arise from meltback etching during the initial growth process. 7 As a result, polycrystalline GaN is formed during the further deposition process. This becomes evident by comparing the two areas highlighted by white rectangles in Fig.…”

“…As a drawback, the growth of GaN structures directly on Si substrates usually causes a high density of threading dislocations and cracks due to strong deviations of the lattice constants and the thermal expansion coefficients. [5][6][7] Hence, the defect characterization is a critical issue for optimization of nitride-based semiconductor devices.…”

Preface

“…As an alternative strategy to overcome the p-type problem, Liu et al [2] reviewed the progress in ZnO-based heterojunction ultraviolet light-emitting diodes (LEDs) and laser diodes (LDs) involving thin films and nanostructures. As important and representative wide bandgap semiconductors, III-nitrides have been widely and deeply investigated [3][4][5][6][7]. In this special issue, some innovations of the growth and processing technologies are laid out; for instances, pulsed metal organic chemical vapor deposition has been developed by Hao et al [3], and hydride vapor phase epitaxy, laser lift-off, and chemical mechanical polishing techniques have been modified in Zhang et al [4].…”

“…Based on their improved techniques, the high-quality materials, such as GaN, InN, InAlN, and AlGaN were obtained, and the corresponding advanced devices, such as high electron mobility transistor, vertical structure LEDs, and LDs, were successfully fabricated. Zhang et al [5] present a very attractive subject, GaN-based optoelectronic devices on Si substrate, which would act as a platform for mature Si-based integrated circuits and even for optoelectrical integration. Besides the typical III-V GaN-based and II-VI ZnO-based compounds, some other wide bandgap semiconductors are also investigated in this special issue.…”