(PHOTO-)ELECTROCHEMISTRY AT n-GaN GROWN ON SAPPHIRE AND ON Si: A COMPARITIVE STUDY

摘要

In this paper, a comparison is made between the (photo-)electrochemical behavior of n-GaN grown on sapphire (n-GaN/sapphire) and n-GaN grown on n-Si (n-GaN/Si). From impedance measurements, it can be concluded that at n-GaN/Si, a distribution of surface states is present, which cannot be observed at n-GaN/sapphire. A difference in the value of the flatband potential of about 0.5V is observed between both layers, reflecting a difference in surface defect structure or a different polarity of the layers. Luminescence experiments show that under certain conditions radiative recombination at (near)surface states occurs at n-GaN/sapphire as well as at n-GaN/Si. However, these (near)surface states are not the same for both layers.