High frequency, high breakdown AlInAs/GaInAs junction modulated hemts (JHEMTs) with regrown ohmic contacts by MOCVD

Abstract

AlInAs/GaInAs High Electron Mobility Transistors excellent high frequency and low noise performance [l]. (HEMTs) have shown However, the power performance of the AlInAdGaInAs channel HEMT has yet to be exploited [2]. The reason is a combination of the lower breakdown voltage in the InGaAs channel and the weak Schottky-barrier height on A M s . On the other hand, the high current densities, due to the large sheet charge density available in the AlInAdGaInAs system make it attractive for millimeter-wave power. Therefore, to optimize the power performance of the AlInAdGaInAs HEMT, the gate barrier height and the breakdown voltage must be improved without sacrificing currcnt density. We present a technology to increase the gatedrain breakdown of AlInAs-GalnAs HEMTs tb record values without substantial impact on other parameters such as Idss and gm. The breakdown in these structures is dependent on the multiplication of electrons injected from the gate (gate leakage) and the source (source cumnt) into the channel. In addition holes are generated by high fields at the drain and arc swept back into the gate and source electrodes. These phenomena can be suppressed by increasing the gate barrier height and alleviating the fields at the drain. In our approach we have achieved both by incorporating a P+ 2DEG junction as the gate which modulates the 2DEG gas and by utilizing a selective regrowth of the some and drain regions by MOCVD. The l p gate-length devices fabricated show a full channel current of 340 “m, transconductance of 240 mS/mm and record high gate-drain breakdown voltage of 3OV (4;~ = l p ) at lmA/mm gate leakage. This is a substantial increase in breakdown with higher c m n t density over devices previously reprted[3]. The extracted unilateral gain cutsff frequency (fmax) was 75 GHz and the measured current gain cut-off fkquency (ft) was 22GHz. The gate e d drain bias dependence of ft and fmax was measured and will be discussed. [l] [2] [31 *