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Polarity determination of InN by using circular photogalvanic effect

Xinqiang Wang 1Qi Zhang 1Bo Shen 1Yonghai Chen 2Yoshihiro Ishitani 3Akihiko Yoshikawa 3

1. State Key Lab of Artificial Microstruct. and Mesoscopic Physics, School of Physics, Peking Univ., Beijing 100871, China
2. Laboratory of Semiconductor Materials Science, Institute of Semiconductors, CAS,, Beijing 100083, China
3. Graduate School of Electrical and Electronic Engineering, Chiba University,, 1-33 Yayoi-cho, Inage-ku, Chiba, Chiba 2638522, Japan

Abstract

To determine lattice polarity is an important issue in InN research since it leads to various differences in growth behaviours and properties such as crystal growth modes, surface stability, and impurity incorporation. In this presentation, a novel way was proposed to determine lattice polarity by using circular photogalvanic effect (CPGE).

In CPGE, a net current was generated without adding any external bias under the irradiation of a circular polarized light. This CPGE current was observed in as-grown InN layers in a magnitude of several nA, Origin of the CPGE can be attributed to lack of spatial inversion symmetry. The former degeneration band splits into two bands with opposite spin indices as symmetry reduced. When the InN layer is radiated by circular polarized light, an asymmetry distribution of excited electrons in momentum space is generated due to optical selection rules, which leads to a net current in the InN.

As a wurtzite semiconductor, InN is lacking of inversion symmetry. Along c-direction, the lattice of In-polarity can be regarded as a complete inversion of that of N-polarity. Thus the spin-orbit interaction in InN with contrary polarities should be opposite, resulting in opposite spin splitting. Therefore, the sign of photocurrent due to CPGE should be opposite for InN layers with different polarities because of the opposite spin splitting. This prediction was then confirmed by the experimental observation that both CPGE photocurrents and their dependences on the incident phase angle are opposite for InN layers with different polarities. Furthermore, it was found that the above phenomenon is independent of conduction type, i.e. both n- and p-type InN shows the same sign of CPGE current and the same dependence on the incident phase angle as well. Therefore, polarity of InN can be easily determined by investigating their CPGE photocurrents.

It should be noted that this method is operated under ambient, technically simple and sample-nondestructive.
 

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Related papers

Presentation: Oral at E-MRS Fall Meeting 2009, Symposium A, by Xinqiang Wang
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-11 07:50
Revised:   2014-10-14 12:41