CRYSTAL ORIENTATION DEPENDENCE OF IMPURITY DOPANT INCORPORATION IN MOVPE-GROWN III-V MATERIALS

We investigated the crystal orientation dependence of impurity dopant incorporation in III-V compound semiconductors grown by metalorganic vapor phase epitaxy (MOVPE). Doping experiments were performed for group-II acceptors (Zn and Mg), a group-VI donor (Se), and a group-VI donor (Si from silane or disilane) into MOVPE-grown GaAs, Ga0.5In0.5P, and (Al0.7Ga0.3)0.5In0.5P. The doping efficiency for each impurity was studied between (100) and (111)A/B faces. Comparing our results to previous reports, we found that there is a general rule in the orientation dependence of impurity incorporation, according to dopant groups. The group-II acceptors (Cd, Mg, and Zn), which reside on the group-III sublattice, are preferentially incorporated on the (h11)A face (h greater-than-or-equal-to 1) and, in many cases, incorporated less on the (h11)B face (h greater-than-or-equal-to 1) than on the (100) face. In all materials, the Zn incorporation is most prominent on the (311)A face. In contrast, the group-VI donors, which reside on the group-V sublattice, are preferentially incorporated on the (h11)B face (h greater-than-or-equal-to 1) and incorporated less on the (h11)A face (h greater-than-or-equal-to 1) than on the (100) face. Comparing to group-II and group-VI impurities, Si generally exhibits weak dependences. Based on rate limiting processes for the dopant incorporation, we constructed a model for the orientation dependence for the group-II and group-VI impurities, considering atomic bonding geometries between adsorbed impurity atoms and adsorption sites.