Low-switching energy resonant-tunneling photodetectors

We report the optoelectronic characteristics of an optically-switched resonant-tunneling diode (ORTD) consisting of a 40 nm n/sup +/ InGaAs cap layer, a 250 nm n/sup +/ InAlAs emitter window, and an AlAs/InGaAs/AlAs DB heterostructure. Under the DB, we have positioned a thick undoped InGaAs absorber layer which serves both to absorb the incident photons and to increase the peak-to-valley voltage swing. In operation with photons of 0.9 eV or higher, the photogenerated electron-hole pairs within this absorber layer screen the applied electric field leading to a reduction in both peak and valley voltage. When biased with a resistor load, this photo-induced voltage shift is used to switch the device from a high-conductance to a low-conductance operating state. Tn contrast to previous demonstrations, we have integrated the ORTD within a microwave package to enable high-speed (Gb/s) optically-induced switching.