2D-subband spectra variations under persistent tunneling photoconductivity condition in tunnel delta-GaAs/Al structures

TL;DR

This study investigates how 2D electron subband spectra in tunnel delta-GaAs/Al structures change under persistent tunneling photoconductivity conditions at low temperatures, revealing two mechanisms affecting the 2DEG states.

Contribution

It identifies and analyzes two distinct mechanisms—potential well broadening and DX-center photoionization—that influence 2DEG spectra under PTPC conditions.

Findings

Unoccupied subbands thicken to the ground state at 4.2 K.

Subband levels shift uniformly at 77 K.

Two PTPC mechanisms are proposed: potential well broadening and DX-center photoionization.

Abstract

2DEG states of Al/$\delta$-GaAs structures were investigated in the persistent tunneling photoconductivity (PTPC) regime at low temperatures. "Thickening" of the unoccupied subbands to the ground state of 2DEG was observed at $T=4.2$~$K$. It was found that there is a uniform shift of the subband levels at $T=77$~$K$. The behavior of the persistent 2D states in tunneling spectra after various illumination and at different temperatures allows us to assume that there are two PTPC mechanisms, namely, the broadening of the potential well profile of the $\delta$-layer and photoionization of the DX-centers.