Sheet carrier concentration and current–voltage analysis of Al0.15Ga0.85N/GaN/Al0.15Ga0.85N double heterostructure hemt incorporating the effect of traps

Abstract

An analytical approach incorporating traps (donor type) in the AlGaN layer at the top and bottom heterointerface is proposed to determine threshold voltage (Vth), net sheet carrier concentration (ns) and drain current in Al0.15Ga0.85N/GaN/Al0.15Ga0.85N double-heterostructure (DH) high electron mobility transistor (HEMT). Generation of carriers in the 2DEG due to detrapping of these donor traps have been thoroughly studied in the present analysis. Due to traps in the upper and lower AlGaN layer, two 2DEG channels formed, such that ns in a DH-HEMT is nearly twice as compared to that obtained in single heterostructure (SH). Due to increased 2DEG density, drain current is more in DH-HEMT as compared to SH-HEMT. The effect of incorporation of these donor traps on Vth, ns and drain current of DH-HEMT as compared to SH-HEMT has been studied. The effect of Al mole fraction, AlGaN layer thickness, mobility, trap concentration and temperature on drain current of DH-HEMT as compared to SH-HEMT has also been studied. The analysis has been performed considering both, undoped structure (in which traps only contribute to 2DEG formation) and a doped structure (in which the traps as well as the donors from the doped layer contribute to 2DEG formation).