Current confinement and leakage currents in planar buried-ridge-structure laser diodes on n-substrate

An electrical device model for the planar buried-ridge-structure laser on n-type substrate is discussed. It takes into account the finite p-type contact resistivity, the two-dimensional current spreading, and the electron leakage current by drift and diffusion. Using this model, the influence of the relevant device parameters on the leakage current in InGaAsP/InP devices emitting at 1.3 mu m is investigated. It is shown that leakage currents are negligible at room temperature if the contact stripe width does not exceed the sum of the active region width and the p-type confinement layer thickness, but they increase markedly with broader contact stripes and with contact resistivities above 10/sup -5/ Omega -cm/sup 2/. The most important parameter influencing the leakage currents is the doping level of the P-InP confinement layer. With a p-type doping level of 1*10/sup 18/ cm/sup -3/, a p-type contact resistivity below 10/sup -5/ Omega -cm/sup 2/ and a contact stripe width of 6 mu m, the model calculations predict a maximum operation temperature exceeding 100 degrees C. This agrees fairly well with experimental data proving that the rather simple planar buried-ridge-structure laser performs as well as more sophisticated devices incorporating current-blocking layers.<
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