Influence of applied electric field on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells

Abstract

The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells (CDQWs) has been investigated by solving Schrödinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition (ISBT) between the ground state and the third excited state (1 odd − 2even) can be equal to zero when the electric fields are applied in asymmetrical AlN/GaN CDQWs, which is related to applied electric fields induced symmetry recovery of these states. Meanwhile, the energy distances between 1 odd − 2even and 1even − 2even subbands have different relationships from each other with the increase of applied electric fields due to the different polarization-induced potential drops between the left and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electric fields in asymmetrical AlN/GaN CDQWs.

Effects of GaN cap layer thickness on an AlN/GaN heterostructure

“…In the past few years the AlN/GaN heterostructure has attracted much attention due to high power and high frequency applications, for it has a large band gap and polarization effects. [1][2][3][4] Despite the excellent material properties, the problems such as surface sensitivity, high leakage current, and easy oxidization have restricted the performances and reliabilities of AlN/GaN devices. [5,6] It is useful to employ a suitable layer to protect the epi-layer in order to solve these problems.…”

Efficient evanescent coupling design for GeSi electro-absorption modulator

“…EA modulators could potentially achieve a large bandwidth and a practical optical bandwidth with a low operating energy. [2][3][4][5][6][7][8][9][10][11] Currently, several silicon-based GeSi or Ge EA modulators adopting either butting coupling or evanescent coupling are being demonstrated. [12][13][14][15][16][17] In contrast to the butting coupling mechanism, an evanescent-coupled structure is more favorable.…”