Intersubband devices from Wide Band Gap II-VI Semiconductors

SHEN Aidong

Department of Electrical Engineering, City College of New York, New York, NY 10031, USA

ashen@ccny.cuny.edu

Zn_xCd_yMg_1-x-ySe-based wide band gap II-VI semiconductor materials and structures with adjustable band gap (direct) energies from 1.66 eV (c-CdSe, RT) to 3.7 eV (ZB-MgSe, RT) have been traditionally used to fabricate optical emitters and detectors in the visible and ultraviolet spectral regions. The materials can be grown lattice-matched on InP substrate with tunable gaps from 2.1 eV to 3.6 eV. For strained-layers and/or with strain compensations, the tunability is even larger. Experiments have shown that, in Zn_xCd_yMg_1-x-ySe-based heterostructures, about 80% of the band offset is in the conduction band. The widely tunable conduction band offset up to a very large value makes the material system potentially a good candidate for intersubband devices working in a wide spectral range (from near IR to long-wave IR), especially those in the short wavelength region (< 4 μm). This talk reviews our recent effort and progresses on the development of quantum cascade (QC) emitters, quantum-well infrared photodetectors (QWIPs), as well as ultrafast all-optical switches with the wide gap II-VI semiconductors.

The materials were grown by molecular beam epitaxy (MBE) in a dual-growth-chamber Riber system. Properties of the materials were assessed by high-resolution x-ray diffraction, photoluminescence, and Fourier transform infrared spectroscopy. Strong and narrow electroluminescence has been observed in the II-VI QC emitters at temperatures up to RT. II-VI QWIPs that working in both mid-wave IR and long-wave IR regions have also been demonstrated.

This work is supported in part by NSF ERC Center MIRTHE (# EEC-0540832), by NSF grant # ECCS-1028364, and by NSF CREST Center CENSES (# HRD-0833180).