Low-distortion AlGaAs/InGaAs power HFETs with quantum-doped graded-like channels

Abstract

We report on the fabrication and characterization of quantum-doped graded-like channel heterojunction field-effect transistors (HFETs) by molecular beam epitaxy (MBE) using a multiple pulse doping technique. The extended equations describing the piecewise doping profiles have been developed to derive the transconductance and second-harmonic to fundamental ratio. It is found that the thickness of depletion width dominates the maximum transconductance and the high doping gradient offers the device linearity. Two HFETs with different doping gradients have been fabricated to elucidate this concept. We obtain the maximum extrinsic transconductance of 165 mS mm −1 . Both have broad plateaus on their transconductance versus gate-to-source voltage profiles. Further, the devices exhibit a gate-to-drain and a drain-to-source breakdown voltage larger than 25 V. The very small output conductance and good pinch-off characteristics indicate good confinement of the electrons in a quantum-doped channel.

Influence of Sinking-Gate on Al0.24Ga0.76As/In0.22Ga0.78As Double Heterojunction High Electron Mobility Transistors

“…The measured maximum f max s are 35, 37, and 37.5 GHz for devices A, B, and C, respectively. The f t and f max seems relatively low but most likely this is due to long gate length as in [5,[12][13]. However, all devices exhibit a f max /f t ratio of > 2.5 due to improved carrier confinement and low output conductance.…”

“…Device C with a 330-℃ annealed gate even displays a much broader plateau in the g m vs. V GS characteristics, showing the best charge control and device linearity of three devices. To further characterize influence of sinking-gate on linearity properties, we express the I D -V GS curve of device C by a 6th order polynomial as follows [13]:…”

Investigation into intermodulation distortion in HEMTs using a quasi-2-D physical model

“…Much less work has been reported on HEMT structures [18], [19]. Work on MESFETs has concentrated on tailoring the doping profile in the active layer such that charge control is linearized as compared with a uniform doping profile.…”

“…This is reflected in the improved linearity of delta-doped structures. Lour et al have extended the concept by introducing delta-doping in the channel of pHEMTs [18]. Most approaches are based on rough approximations to the charge-control in the device.…”

Comparisons between mesa- and airbridge-gate AlGaAs/InGaAs doped-channel field-effect transistors

“…Doped-channel field-effect transistors (DCFETs) have recently received much attention and are considered to be an alternative to the HEMTs and MESFETs [1][2][3][4][5][6]. They generally have an undoped wide-gap layer as the gate insulator and a thin heavily doped narrowgap layer as the channel.…”