Physical Principles of Photocurrent Generation in Multi-Barrier Punch-Through-Structures

The reach-through effect representing close up the space charge regions of two adjacent oppositely biased junctions leads to a sharp exponential increase in current from the bias voltage (Sze et al., 1971). Therefore, this effect was originally found in transistor structures was undesirable. But in the further development of electronics, this effect has found many applications in electronic devices. For example, in barrier injection transit-time diodes as dccurrent bias (Chu & Sze, 1973; Coleman & Sze, 1971; Presting et al., 1994), in static induction transistors as an extra advantageous current to increase the transconductance of the transistor (Nishizawa & Yamamoto, 1978), in low-voltage transient voltage suppressors as a clamp device (de Cogan, 1977; King et al., 1996; Urresti et al., 2005), in JFET optical detectors as a reset mechanism (Shannon & Lohstroh, 1974, as cited in Lohstroh et al., 1981), in IGFET tetrodes as a modulated current flow (Richman, 1969, as cited in Lohstroh et al., 1981), in punch-through insulated gate bipolar transistors (Iwamoto et al., 2002), in gate-fieldcontrolled barrier-injection transit-time transistors and in light injection-controlled punchthrough transistors (Esener & Lee, 1985). Due to the predominance the diffusion processes in structures with reach-through effect (Lohstroh et al., 1981; Sze et al., 1971) characters of the generation-recombination processes in the space charge regions in these structures, as well as non-stationary processes caused by extraction of the majority carriers and formation of the uncompensated space charge in the base layer are still remain unexplored. To prevent the diffusion processes three-barrier structure was developed, in which the flow of both types of carriers in the structure is limited by rather high potential barriers (Karimov, 1991, 1994, 2002). This allowed us to research in such structures the generation-recombination processes in the space charge regions after reach-through, as well as the influence of illumination on these processes. In these structures is found the internal photocurrent gain (Karimov & Karimova, 2003; Karimov & Yodgorova, 2010), which can not be associated with an avalanche or injection processes. Thus, this section is devoted to disclosing the mechanisms of charge transport and the nature of the internal photocurrent gain in multibarrier reach-through-photodiode structures. In this section, is given a brief overview of multibarrier photodiode structures, as well as the results of a comprehensive research of the dark and light characteristics of multibarrier reachthrough-photodiode structures. On the basis of which is proposed model, which explains the mechanism of charge transport and internal photocurrent gain, as well as some future trends.

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