Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 30: Heterostructures, interfaces, and surfaces

HL 30.3: Vortrag

Mittwoch, 14. März 2018, 15:30–15:45, EW 202

Hole carrier profiles at the surface of p-type Ge measured by low-energy muon spin spectroscopy — •Thomas Prokscha¹, Kim Chow², Elvezio Morenzoni¹, Zaher Salman¹, Evelyn Stilp^1,3, and Andreas Suter¹ — ¹LMU, Paul Scherrer Institut, 5232 Villigen, Switzerland — ²University of Alberta, Edmonton, T6G 2E1, Canada — ³Physics Institute, University of Zurich, 8057 Zurich, Switzerland

Macroscopic transport measurements and modelling are usually used to determine the charge carrier profiles across semiconductor interfaces. A local probe technique, capable of detecting the variation in carrier concentration, offers the unique possibility of measuring carrier profiles and manipulation directly without the need of model assumptions. Here we use for the first time the low-energy µ⁺ beam at PSI with tunable energies in the keV range to investigate charge carrier profiles and their manipulation by illumination in commercial p-type Ge wafers at varying mean implantation depths from 10 nm to 150 nm. In p-type Ge with doping levels of 10¹⁵ cm⁻³ and 10¹⁶ cm⁻³ we observed a depletion of holes in the top 150 nm and 50 nm, respectively. The depletion zone can be persistently removed by illumination with blue light due to filling of empty surface acceptor states with photo-generated electrons [1]. By illumination with red light the photo-generated electrons have not sufficient energy to overcome the surface barrier of about 1 eV [1], and a dynamic equilibrium concentration of holes is observed, which increases as a function of depth.

[1] T. Prokscha et al., Sci. Rep. 3, 2569 (2013).