Search

Direct current characteristics of an InGaP /InGaAs pseudomorphic HFET employing low-to-high double doping channels are first demonstrated and compared with the conventional single doping-channel device. Because the lower InGaAs channel is heavily doped and two-dimensional electron gas is formed in this channel, the threshold voltage is extended to -3.7 V. Experimentally, the transconductance within 50% of its maximum value for gate voltage swing up to 4.5 V is achieved in the studied device, which is greater than that of 3.85 V in the single doping-channel device.

A new InGaP/GaAs/InGaAs camel-like gate field-effect transistor with a δ-doped p-channel is investigated. Owing to the p-n depletion of the camel-like gate structure, the considerable conduction band discontinuity at the p-GaAs/i-InGaAs heterojunction, and the confinement effect for holes in the InGaAs quantum well, simultaneously, a large gate turn-on voltage up to 2.3 V is obtained. Experimental results exhibit a maximum extrinsic transconductance of 34 mS/mm and a saturation current density of 233 mA/mm. An extremely broad gate voltage swing greater than 6 V with above 80% maximum transconductance is achieved. The ft and fmax are of 3.2 and 6.7 GHz, respectively.

A high-performance GaN hydrogen sensor fabricated by a Pd-SiO 2 mixture to form a rough sensing surface with pores and nanoparticles is investigated. Hydrogen atoms trapped on the GaN surface and within the mixture form two-dimensional and three-dimensional dipoles, respectively, depending on biased voltages. Thus three sensing regions are found in current-voltage characteristics. The sensing response and barrier-height variation are over 10 7 and 410 mV, which are the highest values ever reported. The response time is as short as 40 s, indicating the proposed hydrogen sensor is very promising for hydrogen detection.

n- and p-channel InGaP/InGaAs doped-channel pseudomorphic HFETs on the identical chip by selectively etching process are first demonstrated. Particularly, the saturation voltage of the n-channel device is relatively small because 2DEG is formed and modulated in the InGaAs strain channel. Experimentally, an extrinsic transconductance of 292 (72) mS/mm and a saturation current density of 335 (−270) mA/mm are obtained for the n-channel (p-channel) device. Furthermore, the integrated devices exhibit broad gate voltage swings for linear and signal amplifier applications.

A novel InGaP/InGaAs/GaAs p-channel pseudomorphic modulation-doped field effect transistor based on p+-GaAs/n+-InGaP/p-InGaP camel-like gate structure is reported for the first time. Owing to the p–n depletion of the camel-like gate and the presence of relatively large ΔEv at InGaP/InGaAs heterostructure, an extremely large gate turn-on voltage, greater than 2 V, is measured. For a 1×100 µm2 device, the experimental results show a maximum saturation current density of −345 mA/mm and a widely broad gate voltage swing, greater than 4 V, with 80% maximum transconductance. Furthermore, the fT and fmax values are 3.1 and 4.8 GHz, respectively.

An Al/sub 0.3/Ga/sub 0.7/As/In/sub 0.15/Ga/sub 0.85/As/GaAs step-doped-channel transistor (SDCT) with anomalous three-terminal-controlled N-shaped negative-differentiaI-resistance (NDR) phenomena has been fabricated and studied. The maximum drain current and peak-to-valley current ratio (PVCR) of 59 and 6.6 mA are obtained, respectively. The high drain current and PVCR can increase the range of potential applications in large signal and logic circuits. The authors believe that the NDR phenomena are attributed to real-space-transfer (RST) and the deep-level electron trapping effect.