Presentation Information
[17a-S4_201-12]Scanning Tunneling Microscopy of Tip-Induced Metastable DX Center Formation at n-type InAs(110) Near-Surface
〇Kiyoshi Kanisawa1 (1.NTT-BRL)
Keywords:
semiconductor,surface,Scanning Tunneling Microcope
In this presentation, formation of metastable donor complexes (DX centers) near the surface due to the tip-induced electric field is reported by using STM observation of n-type InAs surface. At sample bias voltage V > 0 (tip is neutral), positively charged point-like donors are observed below +0.8 V, whereas negatively charged ring-like patterns are observed at around +1.6 V. This result is explained by impact-ionization due to tunnel electrons further accelerated in InAs by the tip-induced electric field. When the electric field strength exceeds the Avalanche breakdown threshold, the quasi-Fermi level of secondary electrons generated by the impact-ionization induces a structural transition of the donor state to a metastable DX center. The ring-like patterns observed in the differential conductance map are explained as an inelastic tunneling phenomenon by the structural transition to the DX center.