Abstract
A self‐consistent Boltzmann‐Poisson‐Schrödinger Solver is used to study the transconductance degradation in high electron mobility transistor (HEMT), which has extensively been reported by both experimental [1]‐[8] and computational [9]‐[ 13] researchers. As the gate voltage of a HEMT device is increased, its transconductance increases until it reaches a peak value, beyond which, the transconductance is degraded rather sharply with further increase in applied gate bias. We previously reported a two‐subband self‐consistent Boltzmann‐Poisson‐ Schrödinger Solver for HEMT. [14] We further incorporated an additional self‐consistency by calculating field‐dependent, energy‐dependent intersubband and intrasubband scattering rates due to ionized impurities and polar optical phonons.[15] In this work, we have used our Boltzmann‐Poisson‐Schrödinger Solver and studied the effects of the intersubband and intrasubband scatterings of electrons, on the transconductance of a single quantum well HEMT device. The results of our simulations exhibit the same pattern reported by others [1]‐[13]. We concluded that the degradation of transconductance of the device with applied gate bias is attributed to the increased intersubband and intrasubband scattering of electrons, and hence to the reduction of electrons velocity in the channel.
Highlights
Recent advances in III-V compound semiconductor growth techniques have resulted in successful development of high speed devices with transconductances ranging from 427 mS/mm in a wn wide 2-D MES-FET [2] to 1740 mS/mm in a 50 nm self-aligned-gate pseudomorphic high electron mobility transistor (HEMT) [8]
As the gate voltage of a HEMT is increased, the transconductance increases until it reaches a peak value, beyond which, the transconductance is degraded with further increase in applied gate bias.[1]-[13] The reasons cited for this degradation include: increase in gate leakage current [1 ], reduction of inversion charge in the channel [6], dislocations [7], decrease in the average electron velocity [8], increase in population of electrons in the donor AlGaAs layer [9], and neutralized donor effect [11]
FIGURE Transconductance as a function of gate bias in a HEMT device calculated by our Boltzmann-Poisson-Schr6dinger Solver (o) with self-consistent scattering rates (o) without scattering rates optical phonons and ionized impurities
Summary
A self-consistent Boltzmann-Poisson-Schr6dinger Solver is used to study the transconductance degradation in high electron mobility transistor (HEMT), which has extensively been reported by both experimental ]-[8] and computational [9]-[ 13] researchers. As the gate voltage of a HEMT device is increased, its transconductance increases until it reaches a peak value, beyond which, the transconductance is degraded rather sharply with further increase in applied gate bias. [14] We further incorporated an additional self-consistency by calculating field-dependent, energy-dependent intersubband and intrasubband scattering rates due to ionized impurities and polar optical phonons.[ 15] In this work, we have used our Boltzmann-Poisson-Schr6dinger Solver and studied the effects of the intersubband and intrasubband scatterings of electrons, on the transconductance of a single quantum well HEMT device.
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