AVS 47th International Symposium
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP6
Implantation of AlAs Etch-Stop Layers by MBE for Recessed Gate P-HEMTs

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: M. Lin, Alpha Industries, Inc.
Authors: G. Zhou, Alpha Industries, Inc.
W. Liu, Alpha Industries, Inc.
M. Lin, Alpha Industries, Inc.
Correspondent: Click to Email
The AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (p-HEMT) has been widely accepted for many high-performance, low cost millimeter-wave applications and high-speed digital circuits. In HEMTs fabrication process, one of the most critical steps is gate recess etching. This is because recess groove profiles have significant influences on the DC and RF performance of devices and integrated circuits as a whole. Wet-chemical etching is a conventional but important approach to conducting recess etching due to its ease of use and its capability to tailor device performance. To precisely control the gate recess process, the implantation of an etch-stop layer into the p-HEMT device structure is highly desirable. AlAs is a traditional etch-stop material to GaAs because of its high etching selectivity (~ 400x) and near perfect lattice match. For a reliable and controllable etching process, a reasonable thick etch-stop is desired. However, due to its large bandgap (~2.2eV) and higher defect density (DX center, for example), thick AlAs layer may cause ohmic contact problem and other side-effects which would degrade the device performance. We report the study of MBE growth of AlGaAs/InGaAs pHEMT structure with double AlAs etch-stop layers. The thickness of the AlAs etch-stoppers ranging from 1.0 to 2.5 nm. The structures were studied by Hall measurement, high-resolution x-ray diffraction, photoluminescence (PL) and photoreflectance (PR). The selective etching behavior was verified by etching profiles of time dependent sheet charge density from Hall measurements. The correlation between the etching selectivity and ohmic contact resistivity, as well as the device performance of the p-HEMT structure was compared for different structures to get the optimum AlAs thickness.