Passivation of GaSb using rare earth oxide Y₂O₃ - a comparative study of Molecular Beam Epitaxy and Atomic Layer Deposition
Y. H. Lin(林延勲)1*, R. L. Chu(朱瑞霖)*2, W. J. Hsueh(薛惟仁)3, K. Y. Lin(林耕雍)1, T. H. Chiang(江宗鴻)2, C. H. Fu(傅千驊)1, G. J. Brown4, T. W. Pi(皮敦文)5, J. I. Chyi(綦振瀛)3, J. Kwo(郭瑞年)6, M. Hong(洪銘輝)1
1Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, Taiwan
2Department of Material Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
3Department of Electrical Engineering, National Central University, Jhongli, Taiwan
4Air Force Research Laboratory, Dayton, Ohio, United States of America
5National Synchrotron Radiation Research Center, Hsinchu, Taiwan
6Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:林延勲,
Intensive research on antimonide-based compound semiconductors has been carried out for the applications of infrared detectors and ultimate CMOS, owing to their wide-range tunable band gap and high carrier mobility. However, inferior native oxide SbOx, which leads to elemental Sb formation, may be the main obstacle to passivate GaSb surface. The formation of elemental Sb during conventional ex-situ process is inevitable, leading to large leakage current and Fermi-level pinning.

Here, to inhibit the formation of the native oxides and elemental Sb, we have effectively passivated GaSb(100) surface by employing arsenic cap layer to protect the surface from being oxidized. Starting with arsenic-de-capped SbOx free surface, MBE-Y₂O₃ and ALD-Y₂O₃ were used to passivate GaSb; MOS-capacitors with the two oxides have shown decent capacitance-voltage characteristics, and low leakage current density, indicating successful passivation on GaSb surface. Different chemical bonding characterized by in-situ x-ray photoelectron spectroscopy (XPS) has been correlated to different capacitance-voltage characteristics. The interfacial trap densities (Dit’s) were further reduced using MBE-Y₂O₃ deposited at 200 ⁰C (200⁰C MBE-Y₂O₃), along with the attainment of record-high performance of the self-aligned inversion-channel GaSb p-MOSFETs, shedding light for the future high-speed, low-power device applications.

*:Contributed equally to this work.

Keywords: GaSb, Molecular Beam Epitaxy, Atomic Layer Deposition, rare earth oxide