Dh. Chow et al., MONOLITHIC INTEGRATION OF RESONANT-TUNNELING DIODES AND HETEROJUNCTION BIPOLAR-TRANSISTORS ON PATTERNED INP SUBSTRATES, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 16(3), 1998, pp. 1413-1416
We report the successful fabrication of coplanar, monolithic integrate
d circuits based on heterojunction bipolar transistors (HBTs) and reso
nant tunneling diodes (RTDs). Molecular beam epitaxy growth of the int
egrated device structure is performed on an InP wafer, which is patter
ned by photolithography and dry etching prior to growth. The substrate
pattern consists of pedestals, which support RTDs after postgrowth de
vice fabrication, and a lower level which ultimately supports HBTs. In
situ sensors for layer thickness (photoemission oscillations) and sub
strate temperature (absorption-edge spectroscopy) play a critical role
in controlling key growth and structural parameters for the HBT and R
TD devices. Utilization of the photoemission oscillation sensor during
deposition of the AlAs barrier layers of the RTD structure has enable
d control of peak currents to a design tolerance of +/-20% for devices
with current densities in the mid-10(4) A/cm(2) range. Implementation
of proportional - integral - derivative control based on a transmissi
on-mo de absorption-edge spectroscopy sensor has enabled regulation of
the substrate temperature to a precision of +/-1 degrees C throughout
deposition of the RTD/HBT structure. (C) 1998 American Vacuum Society
.