Effect of modulation of ultrafast transient carrier dynamics by interface on terahertz signal

Shintaro Yamamoto,Takashi Kita,Osamu Kojima

doi:10.1088/1742-6596/1220/1/012013

Abstract

The carrier dynamics in the nanostructured semiconductors related to the drift and diffusion currents strongly affects the device performance, such as the efficiency of the carrier injection into the active layer. We report on the effects of the photocurrent direction on the THz signals emitted from the GaAs crystal including an interface. The polarity inversion of the signal is caused by the change in photocurrent direction from diffusion to drift. The inversion is not affected by electron lifetimes. These results suggest that measurement of the THz wave is useful to consider the photocurrent direction.

Highlights

The light emitting devices based on the semiconductor quantum dots (QDs), such as the QD lasers in the ultrafast optical telecommunication systems [1,2,3] and the single photon sources in the information communication systems [4,5,6], have been studied
The effects of the potential modulation caused by the latticemismatched strain on the carrier diffusion direction can be revealed by measuring the THz time domain signal [15]
We demonstrate the calculation results of the THz signal emitted from the GaAs crystal including an interface, which causes the potential modulation, near the surface

Summary

Introduction

The light emitting devices based on the semiconductor quantum dots (QDs), such as the QD lasers in the ultrafast optical telecommunication systems [1,2,3] and the single photon sources in the information communication systems [4,5,6], have been studied. The observation of THz time-domain signals emitted from the semiconductor surfaces provides the diffusion direction of carrier excited by the ultrashort pulse lasers [12,13,14]. The effects of the potential modulation caused by the latticemismatched strain on the carrier diffusion direction can be revealed by measuring the THz time domain signal [15]. When the direction of photocurrent in the deeper region is changed, the polarity of the THz signal is inverted. This inversion is discussed from the aspects of the balance between the diffusion and drift, and carrier lifetimes

Calculation method

Results and discussion

Conclusion