Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates

Romain Cariou (1, 2) , Rosa Ruggeri (3) , Xi Tan (1) , Giovanni Mannino (3) , Joaquim Nassar (1) , Pere Roca I Cabarrocas (1)

1 LPICM - Laboratoire de physique des interfaces et des couches minces [Palaiseau]
2 III-V Lab - Alcatel-Thalès III-V lab
3 IMM - Istituto per la Microelettronica e Microsistemi [Catania]

We report on unusual low temperature (175 °C) heteroepitaxial growth of germanium thin films using a standard radio-frequency plasma process. Spectroscopic ellipsometry and transmission electron microscopy (TEM) reveal a perfect crystalline quality of epitaxial germanium layers on (100) c-Ge wafers. In addition direct germanium crystal growth is achieved on (100) c-Si, despite 4.2% lattice mismatch. Defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and threading dislocation density (TDD) values as low as 106 cm−2 are obtained. Misfit stress is released fast: residual strain of −0.4% is calculated from Moiré pattern analysis. Moreover we demonstrate a striking feature of low temperature plasma epitaxy, namely the fact that crystalline quality improves with thickness without epitaxy breakdown, as shown by TEM and depth profiling of surface TDD.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Romain Cariou, Rosa Ruggeri, Xi Tan, Giovanni Mannino, Joaquim Nassar, et al.. Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates. AIP Advances, 2014, pp.077103. ⟨10.1063/1.4886774⟩. ⟨hal-01019905⟩