Research

Surface PV Spectroscopy


Surface photovoltage spectroscopy (a version with contacts) has been used for many years to study the properties of electronic states near the surface in bulk semiconductors. With the advent of crystal growth techniques, allowing the production of high quality semiconductor heterostructures, SPS spectroscopy found additional applications and it was used to study electronic states in heterostructures, quantum wells (QW’s), quantum dots (QD’s) and nanostructures.

We are using a contactless version of SPS . A simple scheme of sample mounting is shown in Fig.1. SPS, like electromodulation techniques (e.g. photoreflectance – PR and contactless electroreflectance – CER), being nondestructive and contactless, but possesses some advantages over PR and CER. For instance, there are no below bandgap oscillations originating from the doped substrates and in which case, the PR or CER techniques may be useless.

The potential of contactless SPS we will show on two examples. First the optical studies of GaAs1-xSbx/GaAs multiple quantum well (MQW) structures with emission close to 1.3 µm are shown. Figure 2 shows a comparison of PR, normalized derivative of SPS - d(E SPS)/dE (DSPS) and piezoreflectance (PzR) spectra for the structure with the antimony content, x = 0.23. Vertical arrows mark the energies corresponding to optical transitions between: confined states and are designed nhh(lh)-1e and confined states in valence band and extended states in conduction band 1hh(lh)-cb. We can conclude that the optical diagnostic tools of PR and SPS are powerful supplementary techniques in the investigations of complicated quantum systems. PR gave detailed information about the heavy-holes related transitions while SPS gave additional information concerning light-holes related ones.

The second is example of SPS investigations of vertically stacked InAs/GaAs QD systems with different spacer layer thickness. In comparison with the PL data (not shown here), SPS spectra showed in Fig.3 present more QD related transitions.

Representative papers

Temperature dependent surface photovoltage spectra of type I GaAs1-xSbx/GaAs multiple quantum well structures
P. Sitarek, J. Misiewicz, Y. S. Huang, H. P. Hsu, K. K. Tiong
J. Appl. Phys. 113, 073702 (2013)
Optical Transitions between Confined and Unconfined States in p-Type Asymmetric GaAs/InGaAs/AlGaAs QW Structures
P. Sitarek, K. Ryczko, J. Misiewicz, D. Reuter, A. Wieck
Acta Physica Polonica A 120 849 (2011)
Optical studies of type I GaAs1-xSbx/GaAs multiple quantum well structures
P. Sitarek, H. P. Hsu, Y. S. Huang, J. M. Lin, H. H. Lin, K. K. Tiong
J. Appl. Phys. 105, 123523 (2009)
Surface photovoltage spectroscopy and photoluminescence study of vertically stacked self-assembled InAs/GaAs quantum dots
P. Sitarek, H. P. Hsu, H. S. Chen, Y. S. Huang, J. S. Wang, C. M. Lai, L. C. Wei, R. S. Hsiao, S. Y. Lin, J. Y. Chi
Proceedings of 5th IEEE Conference on Nanotechnology, Nagoya, Japan, July 2005