Effects of Varying Quantum Well Barrier Height and Quantum Well Number on the Intrinsic Frequency Response of InGaAsP/InP Multiple Quantum Well Semiconductor Lasers

Abstract

This thesis reports on an extensive investigation into the intrinsic frequency response of various MQW lasers as determined from parasitic-free relative intensity noise (RIN) measurements. Eleven structures were designed, grown and fabricated at Nortel Technology's Advanced Technology Laboratory in Ottawa. Five of the laser structures had active regions containing 10 QWs. The barrier layer composition for these structures was varied such that the emission wavelength corresponding to the barrier band-gap increased from 1.0 pm to 1.2 pm in 0.05 pm steps. The remaining six structures had a constant barrier layer emission wavelength of 1.1 pm but the number of quantum wells was varied from 5, 7, 8 to 14 in 2 well steps. In all structures the QWs were embedded in a graded- index-separate-confinement-heterostructure waveguiding region and were strained to 1.0 percent in compression. The devices processed from these structures were Fabry-Perot type lasers having cavity lengths ranging from 254 pm to 1016 pm. Resonance frequency and damping values as a function of injection current and single facet optical power, as well as optical spectra just below threshold, were obtained for over one hundred devices. From this data the response coefficient D, K factor, group velocity (vg), photon energy (hv), mirror loss (am), and internal absorption (aint) were characterized. Using these characterized parameters dg/dN, dg/ds, and the maximum theoretical intrinsic 3 dB bandwidth (fmax) were calculated. The effects of varying QW number, barrier height, and cavity length on all these parameters was investigated. Limitations with using the single mode rate equation model for these characterizations is discussed. As well, potential limitations with the basic design of the structures studied in this thesis as revealed by the results are explored.