Theory of the in-plane photoelectric effect in two-dimensional electron systems

TL;DR

This paper develops a comprehensive theoretical model for the in-plane photoelectric effect observed in 2D electron systems at THz frequencies, enabling better understanding and optimization of THz detectors based on this phenomenon.

Contribution

The paper provides analytical formulas for photocurrent, quantum efficiency, and responsivity of the IPPE effect, applicable across various 2D semiconductor systems.

Findings

Analytical expressions for photocurrent and efficiency derived.

Theoretical predictions match experimental observations.

Applicability extends to multiple 2D material systems.

Abstract

A new photoelectric phenomenon, the in-plane photoelectric (IPPE) effect, has been recently discovered at terahertz (THz) frequencies in a GaAs/Al$_x$Ga$_{1-x}$As heterostructure with a two-dimensional (2D) electron gas (W. Michailow et al., Sci. Adv. \textbf{8}, eabi8398 (2022)). In contrast to the conventional PE phenomena, the IPPE effect is observed at normal incidence of radiation, the height of the in-plane potential step, which electrons overcome after absorption of a THz photon, is electrically tunable by gate voltages, and the effect is maximal at a negative electron ``work function'', when the Fermi energy lies above the potential barrier. Based on the discovered phenomenon, efficient detection of THz radiation has been demonstrated. In this work we present a detailed theory of the IPPE effect providing analytical results for the THz wave generated photocurrent, the quantum efficiency, and the internal responsivity of the detector, in dependence on the frequency, the gate voltages, and the geometrical parameters of the detector. The calculations are performed for macroscopically wide samples at zero temperature. Results of the theory are applicable to any semiconductor systems with 2D electron gases, including III-V structures, silicon-based field effect transistors, and the novel 2D layered, graphene-related materials.