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Threshold current and quantum efficiency of the surface-emitting laser diodes were calculated on the basis of a planar carrier diffusion model with cylindrical boundary and analytical electromagnetic field distribution in either a uniform core waveguide or Vainshtein's open cavity model. Surface recombination at the boundary of the quantum-well active region was much greater than the bulk recombination in both structures unless cavity diameter was greater than 50 /spl mu/m. Diffraction loss was also significant in the open cavity structure as cavity diameter decreased. Reducing the surface recombination velocity leads to the reduction of threshold current and enhancement of differential quantum efficiency. In order to further reduce that current, using a buried heterostructure with a vertical waveguide structure is suggested.

Asymmetry in optical power versus external-cavity length characteristics has been observed in a short-external-cavity laser-diode configuration. It is shown that this phenomenon can be explained only by introducing a complex coupling coefficient, representing the coupled field amplitude into the laser diode at each reflection. This supports the open resonator model description of the short-external-cavity laser diode. Such an asymmetry effect should be recognized and properly dealt with in any laser-diode sensor. >

Under a high-gain operating condition, the presence of a multiplication process in the InGaAs(P) regions of an InP/InGaAsP/InGaAs avalanche photodiode (APD) having a structure of separated absorption and multiplication regions could lead to significant enhancement of the avalanche buildup time. As a result, the bandwidth of the device could be reduced considerably. The dependence of the avalanche multiplication factor and the intrinsic response time on the reverse bias voltage, the heterointerface field, the doping concentrations, and the width of the InP layer is examined in detail for the case in which hole injection is assumed. It is shown, for example, that for a fixed value of doping concentrations, reduction of the excess noise factor and enhancement of the gain-bandwidth product of the device can be achieved at the same time by a proper increase of the width of the InP layer. >

An effective method of two-dimensional transient analysis of potential and charge carrier distribution in a buried-channel charge-coupled device (BCCD) operating in storage and transfer modes has been developed with the aid of the finite Fourier transform (FET) technique. The effect of different clocking schemes on charge carrier transfer inefficiency and charge handling capacity are examined and discussed using the method developed. It is also shown that, for a BCCD operating in the storage mode, two-dimensional analysis indicates that the charge handling capacity determined by one-dimensional analysis can result in overestimation, which is misleading.

Assuming that the temperature dependence of the threshold current for pulsed operation is known, an analytical expression for the maximum heat-sink temperature, T/sub hm/, for CW operation of the laser can be derived. The maximum heat-sink temperature is expressed in terms of the characteristic temperature T/sub 0/, the room-temperature threshold current for pulsed operation I/sub 0/, the equivalent effective thermal resistance theta , and the equivalent effective series electrical resistance r of the device. It is shown that the values of T/sub hm/ can be enhanced by increasing the value of T/sub 0/ or by decreasing the values of I/sub 0/, theta , and r. >

New approximations for the carrier generation rates in silicon under AM1 and AM2 solar illumination are presented. They may simplify the analysis of silicon solar cells, particularly when done by hand.