Abstrakt
The aim of this work is to compare and improve optical and structural properties of GaN layers prepared using TMGa or TEGa precursors. MOVPE grown GaN buffer layers on sapphire substrates are usually grown from TMGa precursor at the temperatures above 1000 degrees C.
These layers contain deep and shallow acceptor levels which are responsible for blue and yellow defect bands in luminescent spectra. Both defect bands are detrimental for all major nitride device applications.
Especially n-doped GaN layers suffer from strong yellow defect bands. In this work, it is shown that yellow band photoluminescence intensity can be suppressed by using TEGa precursor during the growth of n-doped GaN layers.
Different kinds of growth parameters, such as growth temperature or growth rate, have been studied. It is also shown that the change of carrier gas (H-2 or N-2) has very strong influence on the layer quality.
H-2 carrier gas increased intensity of yellow band in sample grown from TEGa precursor while N-2 carrier gas had the same effect for sample grown from TMGa precursor. Variable energy positron annihilation spectroscopy showed creation of single V-Ga in H-2 atmosphere and clustering of V-Ga to big complexes ((V-Ga)(3)(V-N)(n)) in N-2 atmosphere.