Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external ben...

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Bibliographic Details
Published in:Applied physics letters 2015-11, Vol.107 (19)
Main Authors: Shervin, Shahab, Kim, Seung-Hwan, Asadirad, Mojtaba, Ravipati, Srikanth, Lee, Keon-Hwa, Bulashevich, Kirill, Ryou, Jae-Hyun
Format: Article
Language:English
Subjects:
Applied physics
BENDING
Bending machines
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Compressive properties
ELECTRON GAS
ELECTRON MOBILITY
Electrons
Flexible structures
GALLIUM NITRIDES
Heterostructures
High electron mobility transistors
POLARIZATION
RADIOWAVE RADIATION
Semiconductor devices
SEMICONDUCTOR MATERIALS
STRAINS
SUBSTRATES
Tensile strain
THIN FILMS
Threshold voltage
Transconductance
TRANSISTORS
TWO-DIMENSIONAL SYSTEMS
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Summary:This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4935537