Influence of Annealing Condition on Threading Dislocation Density of Ge Grown by RPCVD

Abstract

The influence of annealing conditions on the crystallinity of Ge deposited on Si (001) is investigated. Ge deposited with postannealing at 800°C or 850°C, five cycles of postannealing at 750°C and 850°C and several cycles of annealing at 800°C or 850°C during the Ge growth by interrupting the deposition step (cyclic annealing) are compared. To check the threading dislocation density (TDD) of the deeper part of the Ge layer, thinning by HCl vapor phase etching (VPE) followed by Secco defect etching is performed for 5 µm thick Ge of all annealing variants. By comparing TDD of the same Ge thickness without / with HCl VPE, TDD reduction after VPE is observed for the samples with cyclic annealing process only. In the case of the cyclic annealing process, 5 µm thick Ge shows the same TDD level compared to that with five cycles of postannealing at 750°C and 850°C with lower thermal budget. A lower amount of tilted Ge planes at the interface is confirmed for the sample with cyclic annealing indicating higher crystal quality also in the deeper part of the Ge layer.