Electrical characterization of Si-donor-related shallow and deep states in InGaAlP alloys grown by metalorganic chemical vapor deposition

Donor-related shallow and deep states in Si-doped In_0.5(Ga_1-xAl_x)_0.5P (x = 0.0-1.0), grown by MOCVD, have been systematically investigated. DLTS measurements have revealed deep levels, with a constant thermal emission energy value (E_DLTS = 0.42 eV), for x0.3. The concentration of these levels increased linearly with net donor concentration and reached a maximum at x {reversed tilde equals} 0.5. It was found that these levels become the dominant donor level for conduction electrons in those alloys with x0.3. The electron thermal activation energy, determined by Hall effect measurements, rapidly became larger with increasing Al mole fraction x above x = 0.3. This reached a maximum at x = 0.5, and decreased with increasing the mole fraction over the range 0.5≤x≤1.0. This dependence, of donor states on alloy composition, cannot be explained in terms of the accepted conduction band structure.