High Speed HEMT Memory Device
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
A very fast, high density memory element can be developed by tailoring the doped layer in a high electron mobility transistor (HEMT). The HEMT is a MESFET (metallized semiconductor field-effect transistor) which achieves very high electron mobility in the channel. This is partially due to the physical separation of the conduction electrons from their donor impurities. This effect is achieved by means of a heterojunction comprised of a heavily doped (Nd about 1018Si), wide bandgap semiconductor AlxGal-xAs layer 2 (as seen in Fig. 1) grown epitaxially on top of an undoped, narrow gap semiconductor, GaAs 4. The bandgaps are about 1.7 eV and 1.4 eV, respectively. The conduction electrons 3 are confined to a sheet of charge just below the interface due to this bandgap difference.