Magnetoconcentration-Exclusion Device

The top and the bottom surfaces are chemomechanically treated to ensure low and high surface recombination rate, respectively. Donors are implanted in a thin layer near the positive contact. The bottom surface is mounted to a heat sink. Bias contacts are placed at the begirming of the n and at the end of the v region, and an additional pair of contacts is placed on the top surface of the v region (both within the excluded zone) for the readout of the photosignal. 

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The design of magnetoconcentration photodetectors is very simple, even simpler than an exclusion device. Its basic version is simply a homogeneous slab of narrow-bandgap semiconductor. 

It is only to be expected that some nonequilibrium detector stmctures have their analogs in semiconductor lasers. Exclusion detectors correspond to single-hetero-lasers, extraction devices to double-heterolasers, and magnetoconcentration detectors to lasers with the magnetoelectric photoeffect proposed by Marimoto et al. [331]. This inverse analogy is valid not only in electrical, but also in optical field, where e.g., resonant cavity (RCE) detector structures are connected with VCSEL lasers, and lasers with a PBG cavity with PCE (photonic crystal-enhanced) detectors. 

Approximations usual for the calculation of the frequency response of conventional photonic detectors of optical radiation are not applicable to nonequilibrium detectors, since they operate exclusively under high bias levels. The treatment of magnetoconcentration devices is especially complex in this regard because of the requirement for high magnetic fields. Thus, the approach used here is based on direct numerical solution of the full mathematical-physical model of the device, similarly to the approach to the stationary solution. 

The nonequiUbrium depletion and the increase of dynamic resistance in magnetoconcentration detectors is lower than in the case of heterostructure extraction photodiodes, but significantly better than in exclusion-based isotype devices under similar working conditions (lower dark currents and higher operating temperatures). 

The concept of the magnetoconcentration-extraction combination (or, more accurately, magnetoconcentration-extraction-exclusion) is actually similar to the one described in the above section. Basically, one places a nonequilibrium extraction diode into a crossed electric and magnetic field, as shown in Fig. 3.75. This device could potentially offer the best performance of all nonequilibrium detectors, since it further enhances the operation of the extraction photodiode which already furnished superior performance. 

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