The effect of the buffer layer on the structure, mobility and photoluminescence of MBE grown GaN[Molecular Beam Epitaxy]
Although GaN has been grown mainly by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) offers the advantages of lower growth temperatures and a more flexible control over doping elements and their concentrations. The authors are growing GaN by MBE on sapphire substrates, using a GaN buffer layer to reduce the misfit strain, thus improving the structural quality of the epilayer. The quality of the GaN epilayers (in terms of their photoluminescence, mobility and structure) has been investigated as a function of the buffer layer thickness and annealing time. The investigation showed that increasing the buffer layer thickness improved the mobility of the material because the defect density in the GaN epilayer decreased. Structural characterization by transmission electron microscopy (TEM) showed that the observed increase in the DBE to structural peak ratio in the photoluminescence spectra could be correlated with a decrease in the density of stacking faults in the GaN epilayers. The detailed structure of these stacking faults was investigated by dark field and high resolution TEM. Their effect on the electrical and optical behavior of GaN may be assessed by determining the local change in the dielectric function in the vicinity of individual stacking faults.
- Research Organization:
- Univ. of Cambridge (GB)
- OSTI ID:
- 20104544
- Country of Publication:
- United States
- Language:
- English
Similar Records
New buffer layers for GaN on sapphire by atomic layer and molecular stream epitaxy
Evaluation of AlGaN/GaN high electron mobility transistors grown on ZrTi buffer layers with sapphire substrates