AlGaInP/GaInAs/GaAs Modfet Devices with Self-Aligned P + -GaAs Gate Structure
- PDF / 1,226,298 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 14 Downloads / 145 Views
ABSTRACT A self-aligned fabrication scheme of a novel AlGaInP/GaInAs/GaAs-MODFET device has been developed. Two characteristic features have been incorporated in the device structure: An AIGaInP barrier which provides a larger conduction band offset than the commonly used AlGaAs and a highly carbon-doped p-type GaAs gate structure which supports a very simple fabrication scheme. Using 1/am optical lithography we have fabricated first demonstrator devices with a current gain cut-off frequency of 60 GHz and a power gain cut-off frequency of 140 GHz. In addition, the devices show large gate-drain diode breakdown voltages in excess of 30 V and gate currents as low as 50 nA even at gate-
source voltages of -5 V.
INTRODUCTION Heterostructures incorporating the wide bandgap material (AlxGalx)InP 2 have gained
considerable interest for the fabrication of a variety of optoelectronic h evices. These structures not only expand the spectral range of light emitting diodes and injection lasers into the visible region but also improve the temperature characteristics of injection lasers sig-
nificantly. In addition, some of these devices have promising prospects for becoming mass
products in the near future. Overlooking the experience grown up in this area over the last ten years and encouraged by the successful work on GaInP 2 /GaAs based heterojunction
bipolar transistors in our group [1] and elsewhere [2] it seemed attractive to explore the
potential of AlGaInP heterostructures for fabrication of MODFET devices. Considering the many proposals on this subject already published in textbooks such an undertaking seems to be straightforward. However, this approach is bearing considerable risks in fact, because the data base is quite weak. Particulary, the published band offset data scatter over a wide range, and transport properties as well as maximum available densities of two dimensional electron gases formed at interfaces adjacent to AlGaInP barrier structures have been studied only recently [3] and have not been confirmed until now. In this paper we report on first results of real MODFET devices based on the heterostructure system AlGaInP/GaInAs/GaAs. Beside substituting the conventional A1GaAs barrier structure by AlGaInP we have introduced another structural feature: The Schottky gate structure has been replaced by a heavily carbon doped p+-GaAs structure. Thus the GaAs gate structure in this JFET-like [4] design behaves like a Schottky gate with artificially enhanced Schottky barrier because of the high hole concentrations used. This approach lends easy support to a self-aligned fabrication scheme and has the potential to fabricate devices with quarter micron gate structures by using optical lithography tools only.
329 Mat. Res. Soc. Symp. Proc. Vol. 326. ©1994 Materials Research Society
DEVICE FABRICATION The devices were fabricated from AIGaInP/GaInAs/GaAs layer structures grown on 2 in. (100)-oriented, semi-insulating GaAs substrates by low-pressure metal-organic chemical vapour deposition as described elsewhere
Data Loading...
