Ultra High-Speed Operation of Ultra-Fine GaInAs/InP HBT by Suppressing Recombination Current at Mesa Sidewall

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Measurement of Mesa Sidewall Recombination Current of HBT with Fine Emitter Fabricated by Combination of Dry/Wet EtchingIt has been enabled to fabricate 100 nm wide fine emitter by a combination of electron beam exposure, CH_4/H_2 reactive ion etching and wet etching. Size dependence of current gain of this fine HBT has been compared with that of formerly fabricated HBT only by wet etching. In HBT with 010 emitter sidewall realized by a combination of HCl and CH_3COOH etching solution, dry/wet combination etching process has enabled to obtain current performance even or superior to that obtained by only wet etching and current gain over 50, which is sufficiently large for circuit application, has been realized. Therefore, we could show excellent current performance could be realized even in HBT with fine emitter.Fabrication of High-Speed HBT with Fine Emitter and Metal Wire CollectorFine emitter structure combined with reduction method of base-collector capacitance can reduce base-collector capacitance, and therefore, can realize fast operation of HBT. So, we have introduced a base-collector capacitance reduction method, where buried metal wire has been used as collector, to HBT with sub-micron wide emitter. As results, in a device with an emitter having a width of 0.3 um and a length of 1.5 um, a base-collector capacitance less than 0.1 fF, which is the smallest value among ever reported, has been confirmed and a maximum oscillation frequency f_<max> of 200 GHz has been also achieved. Since at present the device performance is largely restricted by non-intrinsic part of the device, such as contact resistance, a more high-speed operation of HBT can be expected when we introduce, for example, a wiring technique reported by another research groups.