Negative differential resistance in direct bandgap GeSn p-i-n structures

Certain GeSn alloys are group IV direct bandgap semiconductors with prospects for electrical and optoelectronical applications. In this letter, we report on the temperature dependence of the electrical characteristics of high Sn-content Ge 0.89 Sn 0.11 p-i-n diodes. NiGeSn contacts were used to minimize the access resistance and ensure compatibility with silicon technology. The major emphasis is placed on the negative differential resistance in which peak to valley current ratios up to 2.3 were obtained. TCAD simulations were performed to identify the origin of the various current contributions, providing evidence for direct band to band tunneling and trap assisted tunneling.