Drivability Enhancement for AlGaN/GaN High-Electron Mobility Transistors with AlN Spacer Layer Using Si Ion Implantation Doping

Abstract

Although a thin AlN spacer layer between the AlGaN barrier and GaN channel layers effectively increases electron mobility and sheet carrier concentration in a two-dimensional electron gas, the very wide bandgap AlN makes ohmic contacts difficult to form. We overcame this problem using Si ion implantation to attain contact resistance below 2:5 Â 10 À6 cm 2 . Samples without ion implantation had poor ohmic properties. Inserting the thin AlN spacer layer dramatically improved the drain current of high-electron mobility transistors.

Improved recess‐ohmics in AlGaN/GaN high‐electron‐mobility transistors with AlN spacer layer on silicon substrate

“…As summarised by Nanjo et al [10], the insertion of a thin AlN spacer layer between the AlGaN barrier layer and GaN channel layers effectively increases the 2DEG concentration and electron mobility due to the enhanced 2DEG confinement [6,11]. However, due to the insertion of a thin AlN spacer layer in this structure, the potential barrier in the ohmic contact region increases resulting in a significant increase in the contact resistance (R c ) thus making it difficult for sufficient current to flow from the 2DEG in the channel to the source/drain electrodes [7][8][9][10]. Different processing techniques have been used to reduce R c such as, n + -GaN layer [7], recess-ohmic etching [8,9], and Si ion-implantation doping [10].…”

“…To further improve AlGaN / GaN HEMT performance, the insertion of thin AlN interfacial layer was proposed by Shen et al [3] in 2001 and it has widely been used for the demonstration of higher performance devices [6][7][8][9][10]. As summarised by Nanjo et al [10], the insertion of a thin AlN spacer layer between the AlGaN barrier layer and GaN channel layers effectively increases the 2DEG concentration and electron mobility due to the enhanced 2DEG confinement [6,11].…”

“…To further improve AlGaN / GaN HEMT performance, the insertion of thin AlN interfacial layer was proposed by Shen et al [3] in 2001 and it has widely been used for the demonstration of higher performance devices [6][7][8][9][10]. As summarised by Nanjo et al [10], the insertion of a thin AlN spacer layer between the AlGaN barrier layer and GaN channel layers effectively increases the 2DEG concentration and electron mobility due to the enhanced 2DEG confinement [6,11]. However, due to the insertion of a thin AlN spacer layer in this structure, the potential barrier in the ohmic contact region increases resulting in a significant increase in the contact resistance (R c ) thus making it difficult for sufficient current to flow from the 2DEG in the channel to the source/drain electrodes [7][8][9][10].…”

“…However, due to the insertion of a thin AlN spacer layer in this structure, the potential barrier in the ohmic contact region increases resulting in a significant increase in the contact resistance (R c ) thus making it difficult for sufficient current to flow from the 2DEG in the channel to the source/drain electrodes [7][8][9][10]. Different processing techniques have been used to reduce R c such as, n + -GaN layer [7], recess-ohmic etching [8,9], and Si ion-implantation doping [10]. The recess-ohmic process was performed on AlGaN/AlN/GaN heterostructures (HSs) grown on AlN/Sapphire templates [8] and SISiC substrate [9].…”

“…The recess-ohmic process was performed on AlGaN/AlN/GaN heterostructures (HSs) grown on AlN/Sapphire templates [8] and SISiC substrate [9]. Recently, Si implantation was used to achieve the specific contact resistance (ρ c ) value as low as 2.36x10 -6 Ω-cm 2 in AlGaN/AlN/GaN HEMT structure grown on SI-SiC substrate [10]. However, thus far, no reports were available on the recess-ohmic approach on AlGaN/GaN HEMTs on Silicon substrate with AlN spacer layer.…”