Molecular Beam Epitaxy

10Applications of III–V Semiconductors for Mid‐infrared Lasers

Yuichi Kawamura

Graduate School of Engineering, Osaka Prefecture University, Osaka, 599‐8531, Japan

10.1 Introduction

Mid‐infrared semiconductor lasers operating at room temperature with emission wavelengths beyond 2 µm have gathered much interest because of their applications to chemical analyses, remote sensing, the spectroscopic identification of gases with strong absorption lines in this wavelength range (CH₄, CO₂, SO₂, etc.), and biomedicals. This is because many absorption peaks of chemical molecules of various materials exist in this wavelength region. As is well known, in the mid‐infrared wavelength region, it is very difficult to achieve room temperature operation with a low threshold current because of a large Auger effect and/or a large free carrier absorption effect. In addition, the molecular beam epitaxy (MBE) growth of III–V semiconductor materials for mid‐infrared lasers has particular difficulties, because the crystal quality of substrates such as GaSb and InAs is not good enough compared with that of GaAs and InP. Also, many kinds of group V elements (such as As, Sb, and N) are used for quantum‐well active layers, so that the very precise composition control of group‐V elements is necessary.

However, recent developments in epitaxy technology make it possible to fabricate high‐performance mid‐infrared lasers. There are several semiconductor materials which are suitable for mid‐infrared lasers. Among these, ...