Calculated band structure for the two investigated HEMTs. (Depth starts from the AlGaAs barrier layer.)
Measured dc transconductance per millimeter of gate width of the control HEMT (solid line) and the composite-channel HEMT (short dashed line). The drain is biased at .
Breakdown characteristics of (a) control HEMT and (b) composite-channel HEMT measured at various values (inset). Gate leakage current shown as reference.
Frequency dependence of short-circuit current gain and MAG/MSG of the proposed HEMTs at gate and drain voltages given in the figure. Extrapolation of MAG vs log(frequency) at /decade produced maximum frequencies of oscillation of 31.5 and for control HEMT and the composite-channel HEMTs, respectively.
Measured gate bias dependence of and (extracted from MAG using /octave extrapolation) at of drain bias. Both control HEMT and composite-channel HEMT are shown.
Layer stack for two studied HEMTs. Both HEMT structures are identical except for the channel layers. Two quantum well structures are used (a) uniform composition and (b) composite channels.
Comparison of performance of presented HEMTs with various channel schemes. Comparative results of devices with various channel designs are shown.
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