Monolithically integrated transmitters for 1.5 micron optical communication applications.

Development of high performance light sources and integrated transmitters suitable for wavelength-division-multiplexing (WDM) applications requires devices with compactness, cost-effectiveness, low power consumption, and low frequency chirping. Key components in modern transmitters consists of light sources, optical switches, and peripheral driving circuits. This work primarily focuses on the modeling and design, fabrication and characterization of these individual components as well as their integration. New device concepts and designs and state-of-the-art performance characteristics have been achieved. Short-cavity edge-emitting distributed Bragg reflector (DBR) lasers, realized by deep reactive ion etching (RIE) etched DBR mirrors, make ${\sim}10\mu$m long devices feasible and lead to the possibility of realization of true gain-compression limited bandwidth. A low threshold current (4.5mA) and reasonable high modulation bandwidth ($\sim$30GHz) 100$\mu$m long device is demonstrated for the first time. The tunneling injection mechanism in a quantum well laser, which is known to minimize hot-carrier effects, was incorporated into the design of a distributed feedback (DFB) laser for the first time. By fitting the experimental data with the empirical relation for temperature dependence of threshold current, a characteristic temperature T$\sb0$ of 70-120K is obtained at room temperature. For a 300$\mu$m long device, the lowest threshold current is 22 mA and the highest small-signal modulation bandwidth is 7.5 GHz. The temperature tunability is about 1A/$\sp\circ$C. The $\lambda$/4-shifted DFB laser preserves a single-mode operation up to 120mA. Design and characterization of InAlAs/InGaAs MQW quantum confined Stark effect (QCSE) electroabsorption modulators with strained-compensated structure is performed. A novel technique to reduce the photoresponsivity of the device, which is a major problem, by selectively doping the quantum wells with erbium is demonstrated for the first time. In comparison to the conventional devices, a two orders of magnitude reduction in photocurrent responsivity (0.005 A/W) is obtained and this result represents an effective solution to the large power consumption in operating QCSE modulators. Monolithic integration of laser/modulator by coupled-cavity scheme is carried out in the cases of identical and different active regions. This study represents the first detailed investigation of such a scheme. Heterojunction bipolar transistors (HBTs) circuits used to drive the laser and modulator are designed and characterized. The design and analysis of monolithically integrated laser, modulator, and HBT driver circuits are described and discussed.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130618/2/9732213.pd