Bufferless Epitaxial Growth of GaAs on Step-Free Ge (001) MesaSupported by the National Natural Science Foundation of China (Grant Nos. 61975230, 61635011, 61804177 and 11804382), the National Key Research and Development Program of China (Grant No. 2018YFB2200104), Beijing Municipal Science and Technology Commission (Grant No. Z191100004819010), and the Key Research Program of Frontier Sciences, CAS (Grant No. QYZDB-SSW-JSC009).

Abstract

GaAs/Ge heterostructures have been employed in various semiconductor devices such as solar cells, high-performance CMOS transistors, and III–V/IV heterogeneous optoelectronic devices. The performance of these devices is directly dependent on the material quality of the GaAs/Ge heterostructure, while the material quality of the epitaxial GaAs layer on the Ge is limited by issues such as the antiphase domain (APD), and stacking-fault pyramids (SFP). We investigate the epitaxial growth of high-quality GaAs on a Ge (001) mesa array, via molecular beam epitaxy. Following a systematic study of the Ge terrace via an in situ scanning tunneling microscope, an atomically step-free terrace on the Ge mesa measuring up to 5 × 5 μm2 is obtained, under optimized growth conditions. The step-free terrace has a single-phase c (4 × 2) surface reconstruction. The deposition of a high-quality GaAs layer with no APD and SFP is then achieved on this step-free Ge terrace. High-resolution transmission electron microscopy and electron channel contrast image characterizations reveal the defect-free growth of the GaAs layer on the step-free Ge mesa. Furthermore, InAs quantum dots on this GaAs/Ge mesa reveal photoluminescent intensity comparable to that achieved on a GaAs substrate, which further confirms the high quality of the GaAs layer on Ge.