1. Solid State and Photonics Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
2. Quantum Science Research, Hewlett-Packard Laboratories, Palo Alto, California 94304, USA

Correspondence to: Yu-Hsuan Kuo¹ Correspondence and requests for materials should be addressed to Y.-H.K. (Email: yhkuo@stanford.edu).

Abstract

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections¹. Silicon-based optical modulators have recently been successfully demonstrated^{2, 3}; but because the light modulation mechanisms in silicon⁴ are relatively weak, long (for example, several millimetres) devices² or sophisticated high-quality-factor resonators³ have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism⁵, which allows modulator structures with only micrometres of optical path length^{6, 7}. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics⁸, but previous silicon–germanium structures have also not shown strong modulation effects^{9, 10, 11, 12, 13}. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed¹⁴, low-power^{15, 16, 17} optical output devices fully compatible with silicon electronics manufacture.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.