Junctionless FET with Wide Bandgap Barrier for High Electron Mobility
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Solution Overview
Problem
High voltage modulation-doped high electron mobility field effect devices face limitations in performance and reliability due to the dependence on doping density and thickness of wide band gap semiconductor layers, which affect the surface density of two-dimensional electron gas and breakdown voltage.
Innovation Solution
A high-voltage junctionless field effect device is developed with a non-planar quantum well transistor structure, featuring a 2D semiconducting channel layer and a barrier layer made from materials like MoS2, WS2, MoSe2, WSe2, or WTe2, where the energy band gap of the barrier layer is wider than that of the channel layer, allowing for the generation of two-dimensional electron gas at their interface, enhancing electron mobility and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single doped AlGaAs and undoped GaAs heterojunction is used to achieve field effect control, then electron mobility is improved due to quantum confinement, but breakdown voltage is limited by the dependence on doping density and layer thickness
Solution Approach 1:
The invention changes the material composition parameters by introducing InGaAs channel layer with specific indium content (0.1-0.3) and AlGaAs barrier layer with specific aluminum content (0.3-0.5), optimizing the band alignment to achieve both high electron mobility and high breakdown voltage simultaneously
Solution Approach 2:
The invention uses a composite heterostructure consisting of InGaAs channel layer combined with AlGaAs barrier layer, where the two materials work together to provide both high electron mobility through the InGaAs channel and high breakdown voltage through the wide bandgap AlGaAs barrier
2Quantity of substance
If the n-AlxGal-xAs control layer is made thicker and heavily doped for depletion mode operation, then 2-DEG exists even at Vg=0 improving on-state current, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The invention optimizes the barrier layer thickness to a specific range (5-15 nm) and doping concentration (1×10^18 to 5×10^18 atoms/cm³), which allows achieving sufficient 2-DEG density without requiring excessive thickness control precision
Solution Approach 2:
The invention uses moderate doping levels and thicknesses that provide sufficient 2-DEG generation without pushing the manufacturing precision to extreme limits, accepting a balanced performance rather than maximizing single parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed device achieves high electron mobility and reliability by generating two-dimensional electron gas at the interface between the channel and barrier layers, resulting in improved performance and breakdown voltage.
Implementation Method 1
The electrons, two dimensional electron gas, 2-DEG, generated in the thin junction layer, confined by quantum effects to a thin sheet, are free to move along this thin layer without hindrance and interference of doped ionized impurities
Implementation Method 2
a heterojunction formed by modulation-doped channel layer and donor-supply layer
Implementation Method 3
by varying the gate voltage, Vg, to change the depth of hetero-junction potential well, to vary the sheet charge density of 2-DEG
Data Source
AI summary
A structure and a method of fabrication are disclosed of a high voltage junctionless field effect device. A channel layer and a barrier layer are formed sequentially underneath the gate structure. The width of energy band gap of the barrier layer is wider than that of the channel layer. Thus the two dimensional electron gas (2-DEG) generated in the interface between the channel layer and the barrier layer of this junctionless field effect device has higher electron mobility. The structure of the device of this disclosure has a higher breakdown voltage which is advantageous for a high voltage junctionless field device. The structure offers advantages in device performance and reliability.