Single Gate HEMT Research Articles

Performance Analysis of Normally-on Dual Gate Algan/Gan Hemt

This paper presents the novel normally-on dual gate (DG) AlGaN/GaN high electron mobility transistor. At high frequency, the dual gate structure gives superlative immunity over short channel effects. Multiple 2DEG channel regions in dual gate AlGaN/GaN HEMT improves the transport characteristics, charge control and gives better linearity. The high carrier mobility and electron saturation velocity contribute to the high switching frequency of DG HEMT. The drain characteristics of single gate HEMT and dual gate HEMT are compared and DG HEMT outstands in drain current. The various analog and linearity parameters are investigated for DG HEMT. The performance analysis provides better transconductance, capacitance, cut off frequency, subthreshold slope and on-resistance simulations represents the potential of DG HEMT. The DG HEMT provides 1100 mA/mm ION, 550 mS/mm transconductance and 11 GHz cutoff frequency at Vgs = 2 V. The high drain current, better transconductance and cutoff frequency results in better sensitivity of device.

Nanoscale dual-gate InAlAs/InGaAs HEMT with improved characteristics

ABSTRACT This paper deals with the DC and Radio Frequency (RF) characteristics of InAlAs/InGaAs-based dual-gate high-electron-mobility transistor (DG-HEMT) for a 50 nm gate length. In single-gate HEMT (SG-HEMT), the gate length having less than 100 nm shows poor transconductance (g m ) which reduces the voltage gain (A v ) and maximum oscillation frequency (f max). To overcome this problem, a dual-gate structure is designed keeping the device dimensions unchanged and a numerical model is developed to study the effect of the dual gate. A comparative study of SG-HEMT and DG-HEMT is presented. For a DG-HEMT, a maximum drain current (Ids ) of 310 mA/mm at Vds = 0.1 V, a peak transconductance (g m_max) of 2294 mS/mm, a cut-off frequency (fT ) of 100 GHz and a maximum oscillation frequency (f max) of 270 GHz have been achieved. For reduced gate length, the DG-HEMT performs better due to the presence of dual gate and double heterojunction.

Microwave performance enhancement in Double and Single Gate HEMT with channel thickness variation

In Single Gate HEMT (SGHEMT) shortening of gate length ( L g ) below 100 nm leads to reduction in Transconductance ( g m ) , which reduces the unloaded voltage gain ( g m / g d ) of the device, thereby reducing the maximum frequency of oscillation ( f m a x ) . The main reason for this reduction in g m with L g in the Single Gate HEMT (SGHEMT) is its inability to maintain the desired channel aspect ratio ( α ). At such a miniaturization level, α not only depends on the channel depth ( d ) but also on the channel thickness ( d c ) of the device [5]. Moreover, the variation of d c may switch the device characteristics from quantum regime to classical regime [27,28]. The Double Gate HEMT (DGHEMT) [22,23] has emerged as a solution for further reduction in L g and provides enhancements over SGHEMT by virtue of its double gate and also for same d c due to double heterojunctions, which virtually increases the value of α . In the present work, extensive simulation work has been carried out using ATLAS device simulator [35] in order to study the effect of d c and L g on DGHEMT and SGHEMT. An analytical model has also been proposed for SGHEMT and DGHEMT to incorporate the effect of variation of d c and L g .

A high-performance Ka-band monolithic variable-gain amplifier using dual-gate HEMTs

The author describes the excellent performance of a Ka-band monolithic variable-gain amplifier monolithic microwave integrated circuit (VGA MMIC) using dual-gate AlGaAs-InGaAs pseudomorphic high electron mobility transistors (HEMT's). The dual-gate HEMT can be fabricated by the same process as a single-gate HEMT. To achieve low-noise performance, a single-gate HEMT is employed in the first stage of the VGA MMIC. However, in the second and third stages, dual-gate HEMT's are used for gain control performance with higher gain. The VGA MMIC achieves more than 30-dB gain with more than 50-dB gain control range from 30 to 35 GHz. A noise figure of 1.4 dB with an associated gain of 29.2 dB is achieved at 33 GHz when biased for a low-noise performance.