Thermal oxidation rates of Al(x)Ga(1-x)As in H(2)O vapor and oxide-defined vertical cavity surface emitting laser characteristics

The incorporation of oxides into semiconductor structures formed by the thermal oxidation of {dollar}rm Alsb{lcub}x{rcub}Gasb{lcub}1-x{rcub}As{dollar} in water vapor has resulted in a marked improvement in device performance. Vertical cavity surface emitting lasers (VCSEL's), in particular, have benefited from this technology, demonstrating record operating characteristics. This study focuses on the following areas with respect to oxide defined VCSEL's: the establishment of rate laws for the lateral oxidation of AlAs, the fabrication of VCSEL's, and the characterization of VCSEL's designed for high speed operation.; An oxidation rate study was conducted on structures with AlAs oxidation layers. At low temperatures and short oxidation times, oxidation was found to be reaction rate limited. Conversely, diffusion across the oxide was determined to be the rate limiting mechanism at high temperature or long oxidation times. The observed rates can be modeled by rate equations by which the two component mechanisms can be separated. An activation energy of 1.6 eV and 0.8 eV was determined for the reaction and diffusion limited mechanism, respectively.; A reduction in oxidation rates was observed with decreasing oxidation layer thickness and increasing doping concentration. The thickness dependence can be incorporated into the rate equations by assuming an oxidation reaction rate which is inhibited by the presence of strain in thin layers. The reaction rate can be characterized by a threshold thickness for which a value of 20 nm was determined for {dollar}rm Alsb{lcub}x{rcub}Gasb{lcub}1-x{rcub}As.{dollar}; Oxide defined GaAs VCSEL's varying in size and oxidation layer composition were fabricated. Threshold currents of 450 {dollar}mu{dollar}A and external differential quantum efficiencies of 0.5 were obtained.; Finally, the large signal modulation characteristics of oxide defined VCSEL's were investigated. A threshold carrier lifetime of 1.6 nanoseconds VCSEL's was determined from laser turn-on delay measurements. The laser turn-on delay was also measured under various driving conditions of interest for digital modulation systems. For applied step voltage values exceeding 3V, data transmission rates exceeding 1 Gbit/sec can be obtained without bias or pattern dependent jitter. Gain switching characteristics were also examined, and short optical pulses with FWHM pulse widths of 13 picoseconds were observed.