Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 44: Poster Session I

HL 44.46: Poster

Tuesday, March 15, 2011, 18:00–21:00, P3

Lithography Optimization on HgTe — •Luis Maier, Mathias J. Mühlbauer, Bruno Krefft, Jiango Yang, Hartmut Buhmann, and Laurens W. Molenkamp — Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg

Mercury telluride (HgTe) has become more and more important in recent years due to its topological insulator properties [1,2]. However lithographical processing is still challenging because HgTe cannot endure temperatures over 100° C and in addition mercury forms numerous alloys with various elements. Here, we present recent developments which helped to improve the fabrication of HgTe nanostructures.

Titanium (Ti) etch masks are commonly used for lithographical processes. Unfortunately, Ti reacts as well with Hg and thus influences the sample quality and the efficiency of gate electrodes. To address this problem we introduced in an additional process step a 10 nm thick SiO2 layer to separate the Ti from HgCdTe top layer. Furthermore, thermal indium bonding has been used till recently to provide ohmic contact to the buried two-dimensional electron gas in HgTe quantum well structures. This process is disadvantageous because In contact require a lot of space and the contacting depth is uncontrollable which prevents the use of back gates. A process for evaporated Gold-Germanium contacts has been developed which gives a certain control of the doping depth and additionally can be used with ultrasonic bonding which reduces the required size of the bonding pads by a factor of 3.

[1] M. König et al., Science, 318, 766, (2007)

[2] A.Roth et al., Science 325, 294 (2009)