| Semiconductor technology provides a great variety of novel devices for chemical sensing applications. This dissertation covers the development two different approaches for realizing devices structure, relevant to chemical sensing applications, (1) an LED based approach used to investigate how semiconductor/chemical surface interactions impact light emission, and (2) dilute nitride quantum-well (QW) diode lasers emitting in the near-infrared (IR) region which can serve as compact light sources employing conventional GaAs or InP substrates for sensor systems. A dilute nitrogen content (<2%) in a QW induces an emission wavelength extension with bandgap bowing at 100-150 meV/ at. % N. In this thesis, we address previously unresolved issues regarding InGaAsN material epitaxy for wavelength extension and optimization, device performance characteristics, and related device physics associated with nitrogen incorporation. High-performance long wavelength single-quantum well InGaAsN lasers (lambda=1380-1410-nm) grown by metalorganic chemical vapor deposition (MOCVD) have been realized with record low threshold current densities. Analysis indicates that carrier transport in the separate confinement region of the laser structure play an important role in performance of dilute nitride lasers. Detailed device characterization, in collaboration with several different research groups, has been performed to study the effects of QW nitrogen content on device characteristics and physics, including temperature dependence of current injection efficiency, high frequency modulation response, effective differential gain, linewidth enhancement factor, radiative efficiency, and the dependence of optical gain on radiative current density. These studies shed new light on the underlying physics of dilute-nitride QW lasers. Design studies on the InGaAs(N)-GaAsSb type-II "W" QW structures were conducted for wavelength extension beyond that achievable with conventional type-I InGaAsN QWs. Experimental studies were conducted, confirming the type-II nature of the optical transition in these structures and demonstrating near-IR emission from GaAs-based "W" QWs and mid-IR emission from InP-based "W" QWs. |
