5.1 Introduction

Compound semiconductor light-emitting diodes and lasers have become the mainstay of present-day fiber optic communication systems. Semiconductor lasers have become essential to current local area networks (LANs) and long-haul intercontinental fiber optic networks [1]. Low threshold current, high output power and efficiency, temperature-independent operation, large modulation bandwidth, low chirp, and wide spectral tunability are some of the properties desirable in a high-performance semiconductor lasers. The use of gain media with reduced dimensionality, in particular QWs, has greatly enhanced laser performance, particularly due to the modification of the band density of states and the resulting gain and differential gain [2, 3].

Many of the properties mentioned are degraded due to hot carrier effects, slow carrier relaxation rates, and carrier leakage over heterobarriers in the active region of the laser [4 6]. It has been known for a while that incorporation of QDs in the active region of optoelectronic devices would drastically improve device performance, primarily due to the enhanced carrier density of states [7]. A large density of states is highly desirable for optoelectronic devices such as lasers and detectors. As one goes from a bulk material, in which there is no quantum confinement, to a system in which the carriers are confined in one dimension (QWs), two dimensions (QWRs), or in all three dimensions (QDs), the density of states function increases in magnitude and becomes discrete.

The fabrication of device-quality QDs has been...