n-p-n silicon lateral phototransistors for hybrid integrated optical circuits

An etched mesa silicon lateral phototransistor (EMS-LPT) suitable for detecting the light signal from optical channel waveguides has been designed and fabricated. In this paper both n
⁺
-p-n
⁺
uniform base and n
⁺
-p-p
^-
-n
⁺
double-diffused EMS-LPT's are reported. The photoactive region of the EMS-LPT is highly localized and can be easily coupled either via an evanescent field or to a grating coupler on a channel waveguide. Light coupling, gain, speed, and signal-to-noise ratio of the device are thereby greatly improved. The fabrication techniques of the EMS-LPT's are compatible with those of MOSFET's, permitting integration of multiple EMS-LPT's and MOSFET load transistors to form optically addressed inverters on the same silicon chip. By flip-chip bonding LiNbO
3
and silicon substrates and coupling LiNbO
3
channel waveguides to EMS-LPT's via grating couplers, we produce electrooptic switches with optical input and output.