Impact of structural modification by spacer layer inclusion on AlGaN/GaN HEMT performance

In this paper, Performances are analyzed of an AlGaN/GaN-based High Electron Mobility Transistor for different device structures. As the 2DEG well forms in the interface of two different bad gap material in HEMT is not infinite energy potential well. Thus there will be a probability of electron carriers appearing outside of the 2DEG well in the barrier layer where they scatter due to impurity. This scattering limits the performance of the HEMT device. Structural Change is based upon a new undoped AlGaN layer between channel and barrier layer in conventional HEMT to reduce the scattering. The impact of this structural change on AlGaN/GaN HEMT performances are compared with respect to the performance of conventional HEMT devices. For both devices, DC and RF performances are observed and results are considered for comparing their performance. Transconductance, drain current characteristics are the DC parameters of HEMT devices which significantly improved after adding the spacer layer. As well as transfer characteristics, output conductance increases significantly. For HEMT with a spacer layer, it is observed that the maximum cutoff frequency is 1.344 times of the HEMT device without a spacer layer. The maximum frequency of oscillation increases by 1.162 times with the addition of the spacer layer. At the same operating condition, the minimum noise figure of the HEMT device decreases after adding the spacer layer. These results prove that the RF performance of HEMT with spacer layer is much better than a HEMT without spacer layer & HEMT with this new device structure is more preferable for high-frequency operations.