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1.55 μm AlGaInAs strained MQW laser diodes


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/10414

1.55 μm AlGaInAs strained MQW laser diodes

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dc.contributor.author Yang, Chi
dc.date.accessioned 2010-02-19T20:30:08Z
dc.date.available 2010-02-19T20:30:08Z
dc.date.issued 2010-02-19T20:30:08Z
dc.date.submitted December 2009
dc.identifier.uri http://hdl.handle.net/1928/10414
dc.description.abstract At the 1.55 µm eye-safe, telecommunications operating wavelength, semiconductor diode lasers must have low threshold currents and operate at high temperatures without thermoelectric coolers. Existing diode lasers in this wavelength range based on the GaInAsP/InP materials system are very sensitive to operating temperature. To obtain high temperature, high power 1.55 µm semiconductor diode lasers, the AlGaInAs/InP materials system with strained quantum well (QW) active regions was investigated with the goal of improving temperature performance. A set of lasers with active regions consisting of different numbers of QWs (2 to 4) and different QW strains (1.2% and 1.6%) were designed taking into account the quaternary alloy bandgap of AlGaInAs, the effect of strain on the bandgap, and the quantum size effects within the QW. The active region growth temperature was optimized using photoluminescence intensity. The wafers were first processed into broad-area lasers and measured under pulsed injection. The characteristic threshold current temperature, T0, for all AlGaInAs lasers was higher (60-70 K) than for GaInAsP lasers. No strong dependence of temperature parameters on strain was observed, while properties varied significantly with the number of QWs. With more QWs, both internal efficiency and T0 increases, but internal loss increases, reducing the characteristic temperature of the differential efficiency T1. The results show that uncooled laser operation at 1.55 µm is very promising with strained AlGaInAs QWs. Ridge waveguide devices demonstrated low threshold and high output power as well as good temperature performance under continuous wave operation. Devices with different ridge heights were fabricated from one wafer and their performance was compared. It was found that current spreading was significant in these devices and a simple current density-versus-applied voltage analysis was developed to determine the spreading factor. The analysis shows that the current spreading was not effectively limited until etching went below the doped cladding layer. A recombination coefficient analysis was performed to investigate the effect of strain on Auger recombination predicted by theory. An indirect method to infer both the nonradiative recombination coefficient and the Auger recombination coefficient was initially used. The measured values of the recombination coefficients were consistent with theoretical predictions and measurements based on other material systems. The Auger recombination was lower than expected, indicating that Auger recombination is reduced in these strained QWs. To understand the carrier dynamics, impedance measurements were carried out for the first time in AlGaInAs strained QW lasers. A small-signal, sub-threshold equivalent circuit model was derived from the laser rate equations to model the measured laser impedance. Several characteristic carrier lifetimes were obtained directly from these electrical impedance measurements. From the temperature dependence of the QW escape time, it was found that hole rather than electron leakage is dominant in the AlGaInAs system due to the relatively low valence band offset. This may explain why the improvement of T0 in AlGaInAs QW 1.55 µm active regions is limited. en_US
dc.language.iso en_US en_US
dc.subject 1.55 μm en_US
dc.subject laser diodes en_US
dc.subject AlGaInAs en_US
dc.subject strained QW en_US
dc.subject Auger recombination en_US
dc.subject hole leakage en_US
dc.subject impedance measurement en_US
dc.subject.lcsh Semiconductor lasers.
dc.subject.lcsh Quantum wells.
dc.subject.lcsh Auger effect.
dc.title 1.55 μm AlGaInAs strained MQW laser diodes en_US
dc.title.alternative AlGaInAs strained MQW laser diodes, 1.55 μm en_US
dc.type Dissertation en_US
dc.description.degree Electrical Engineering en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Electrical and Computer Engineering en_US
dc.description.advisor Malloy, Kevin
dc.description.committee-member Eliseev, Petr
dc.description.committee-member Lester, Luke
dc.description.committee-member Sheik-Bahae, Mansoor

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