35-GHz performance of single and quadruple power heterojunction HEMT's

The potential of single hetrojunction (SHJ) and quadruple heterojunction (QHJ) HEMT devices to provide power amplification at the
Ka
-band frequencies has been measured. The power level observed, from QHJ devices that have gate lengths of 0.5 µm and gate widths of 200 µm, has been over +20 dBm when gain is compressed below the small signal level by 2 dB. The small-signal gain was 5.2 dB at 35 GHz. The power level demonstrated by the SHJ devices is lower than that of the QHJ devices due to the lower "two-dimensional electron gas" sheet carrier density. Our measurements have shown a saturated power level of +15.3 dBm devices of the same geometry as the above-mentioned QHJ devices. The power performance in both cases (QHJ and SHJ) has been obtained with high efficiencies of 38 and 21 percent, respectively. These performance data represent the highest levels of gain and power reported at
Ka
-band frequencies from transistors that employ a 0.5-µm geometry.