Native point defects in Culn(1-x)Ga(x)Se(2): hybrid density functional calculations predict the origin of p- and n-type conductivity

作者：Bekaert J^*; Saniz R; Partoens B; Lamoen D

来源：Physical Chemistry Chemical Physics, 2014, 16(40): 22299-22308.

DOI：10.1039/c4cp02870h

We have performed a first-principles study of the p- and n-type conductivity in Culn(1-x)Ga(x)Se(2) due to native point defects, based on the HSE06 hybrid functional. Band alignment shows that the band gap becomes larger with x due to the increasing conduction band minimum, rendering it hard to establish n-type conductivity in CuGaSe2. From the defect formation energies, we find that In/Ga-Cu is a shallow donor, while V-Cu, V-In/Ga and Cu-In/Ga act as shallow acceptors. Using the total charge neutrality of ionized defects and intrinsic charge carriers to determine the Fermi level, we show that under In-rich growth conditions In-Cu causes strongly n-type conductivity in CuInSe2. Under increasingly In-poor growth conditions, the conductivity type in CuInSe2 alters to p-type and compensation of the acceptors by In-Cu reduces, as also observed in photoluminescence experiments. In CuGaSe2, the native acceptors pin the Fermi level far away from the conduction band minimum, thus inhibiting n-type conductivity. On the other hand, CuGaSe2 shows strong p-type conductivity under a wide range of Ga-poor growth conditions. Maximal p-type conductivity in Culn(1-x)Ga(x)Se(2) is reached under In/Ga-poor growth conditions, in agreement with charge concentration measurements on samples with In/Ga-poor stoichiometry, and is primarily due to the dominant acceptor Cu-In/Ga

• 出版日期2014-10-28