Abstract
The electrical and optical properties of 
and 
prepared by molecular beam epitaxy have been studied. Epitaxial growth was found to take place at ≳ 250°C for 
on 
and 
and at ≳ 300°C for 
on 
; the epitaxial growth ceased at 
for 
and at 
for 
because of the reevaporation of compound and/or impinging molecules. The observed growth rate dependence on substrate temperature and on impinging rate ratio has been explained on the basis of a model in which the number of incorporated and reevaporated molecules are strongly coverage dependent.
on 
, and 
on 
and 
had good mirror smooth surfaces. 
on 
and 
, however, had a rather rough surface. Ga was found to diffuse, due to a large number of misfit defects at 
interface, from the 
substrate into 
influencing the electrical and optical properties of grown layers considerably. The resistivities of undoped layers were ∼5 Ω‐cm for 
on 
and ∼104 Ω‐cm for 
on 
. Sb was used to increase the hole concentration of 
on 
up to ∼1018cm−3. The resistivities of 
on 
were found to decrease to ∼0.07 Ω‐cm by Ga doping. The results of photoluminescence measurement suggest that the higher substrate temperature makes the better quality layers.