Carbon doping characteristics of GaAs and Al 0.3Ga 0.7As grown by atmospheric pressure metalorganic chemical vapor deposition using CCl 4

Abstract

This paper presents the results of a Van der Pauw-Hall analysis of the carbon doping characteristics of GaAs and Al 0.3Ga 0.7As epilayers grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD) using carbon tetrachloride (CCI 4). It also describes the effects of rapid thermal annealing (RTA) on the electrical properties of CCI 4-doped GaAs. Heavily CCI 4-doped GaAs and Al 0.3Ga 0.7As epilayers with a wide range of hole concentrations were obtained by varying the growth temperature from 500 to 750°C and by varying the V/III (AsH 3/TMG) ratio from 5 to 20 while keeping the flow rate of CCI 4 constant. CCI 4-doped GaAs epilayers with hole concentrations between 3.5 × 10 17 and 8.95 × 10 19 cm -3 were obtained under the above growth conditions with constant TMG flow rate. CCI 4-doped Al 0.3Ga 0.7As epilayers have higher hole concentrations than CCI 4-doped GaAs epilayers for various growth temperatures at the same V/III ratio and CCI 4 flow rate, and the hole concentration increases with decreasing growth temperature. The CCI 4-doped GaAs epilayers have nearly the same Hall mobilities as GaAs C-doped by V/III ratio control, but higher mobilities than Zn-doped GaAs. Our results show that the free hole concentration is heavily CCI 4-doped GaAs epilayers increases after RTA at 790°C. This can be attributed to the decrease in the concentration of the hydrogen atoms caused by the breaking of the C-H or C-H x bonds. After longer annealing at 790°C the hole concentration decreases and the hole mobility increases. It is suggested by the increase in free hole concentration by RTA that the activation efficiency of the incorporated carbon in the as-grown CCI 4-doped GaAs epilayers is incomplete.