A novel InAlAs/InGaAs layer structure for monolithically integrated photoreceiver

We present a novel InAlAs/InGaAs layer structure for monolithically integrating MSM diodes and HEMTs into an photoreceiver. The novel layer system, grown on semiinsulating InP, consists of a typical HEMT layer sequence with an additional lattice matched InGaAs layer under the 2DEG channel of the HEMT. This additional layer acts as a photoabsorption layer and enables the production of integrated MSM/HEMT circuits without an additional epitaxial or technological step. Our investigations showed a minor influence of a varying absorption layer thickness on the behavior of the HEMT, leading to a 30% decrease in f/sub T/ and f/sub max/. A 300 nm gate length HEMT can be produced with f/sub T/=75 GHz and f/sub max/=105 GHz on a layer sequence with 200 nm absorption layer thickness. The MSM diodes with a finger width and distance of 500 nm show a bandwidth of about 20 GHz and a responsivity of 0.4 A/W on the same system. On the novel layer system, a monolithically integrated photoreceiver, consisting of an MSM diode and a distributed amplifier (two HEMTs) with a response of 0.7 A/W and a bandwidth of 13.5 GHz is presented.