Abstract: A monolithically integrated heterojunction bipolar transistor optoelectronic transimpedance amplifier using the first transistor as an optical detector. An edge illuminated epilayer waveguide phototransistor is used as the light-detecting element. The phototransistor is used as an optical detector in which the incident light pulses are converted to electrical pulses and then amplified for further signal processing. The phototransistor is monolithically integrated on the same material substrate as the emitter follower amplifier so that the parasitics normally associated with receiver circuitry are minimized. By eliminating the parasitic impedances, the circuit can be used as a receiver in high bit rate optical communication systems.

Abstract: An edge illuminated epilayer waveguide phototransistor including a subcollector layer formed from an epitaxially grown quaternary semiconductor material, such as heavily doped InGaAsP. A collector region of undoped InGaAs is epitaxially grown on the subcollector layer. A base region of moderately doped InGaAs is epitaxially grown on the collector layer. An emitter region, including a doped InGaAsP layer, a doped InP layer, and a heavily doped InGaAs emitter contact layer, is epitaxially grown on the base layer. The various layers and regions are formed so as to define an edge-illuminated facet for receiving incident light. Also, the base does not have an ohmic contact so that the base thickness can be minimized. Finally, the base doping concentration is minimized so that the gain-bandwidth product can be maximized.

Abstract: A monolithically integrated heterojunction bipolar transistor optoelectronic transimpedance amplifier using the first transistor as an optical detector. An edge illuminated epilayer waveguide phototransistor is used as the light-detecting element. The phototransistor is used as an optical detector in which the incident light pulses are converted to electrical pulses and then amplified for further signal processing. The phototransistor is monolithically integrated on the same material substrate as the emitter follower amplifier so that the parasitics normally associated with receiver circuitry are minimized. By eliminating the parasitic impedances, the circuit can be used as a receiver in high bit rate optical communication systems.

Abstract: A metal-semiconductor-metal photodetector (18) is provided including an optical waveguide (22) disposed on a substrate (28) and an array of metal-semiconductor-metal photodiodes (20) coupled to the optical waveguide (22). An absorber (30) is disposed between the photodiodes (20) and the optical waveguide (22) and a transmission line (26) is coupled to the photodiodes (20). Each of the photodiodes (20) includes an electrode (24) having a plurality of interdigitated electrode fingers (31) wherein a width of each finger (31) and a gap between adjacent fingers (31) tapers from one end of the electrode (24) to the other. Preferably the rate of tapering corresponds to an exponential rate of optical power decay through the photodiode (20). In this way, both the photocurrent density in the fingers (31) and the uniformity of the electric field underneath the electrodes (24) are optimized.