III-Nitride Vertical Hot Electron Transistor With Polarization Doping And Collimated Injection
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Solution Overview
Problem
III-nitride-based hot electron transistors (HETs) have been limited in performance compared to competing technologies, particularly in achieving high gain and current density for high-speed, high-power applications due to issues like impurity scattering and low current density.
Innovation Solution
A hot electron transistor design featuring a polarization-engineered emitter stack with a triangular quantum well and an undoped base, utilizing atomic layer etching for low base access resistance, and a graded AlGaN emitter with a tunneling barrier to achieve high current collimation and gain, resulting in a collector current density greater than 440 kA/cm2 and common-emitter gain greater than 75.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If base doping is used to increase current density, then current density improves, but gain deteriorates due to impurity scattering
Solution Approach 1:
The patent extracts and removes the base doping entirely, creating an undoped base region. This eliminates impurity scattering in the base while maintaining high current density through the engineered emitter structure with triangular quantum well and polarization doping, resolving the contradiction between current density and gain
Solution Approach 2:
The patent introduces a triangular quantum well in the emitter as an intermediary structure that enables high current density injection without requiring base doping. The quantum well confines and directs electrons into the base, achieving high productivity without the harmful impurity scattering that would reduce reliability
2Reliability
If base thickness is reduced to improve gain, then gain improves, but current density deteriorates
Solution Approach 1:
The patent performs preliminary action by engineering the emitter structure with triangular quantum well before electrons enter the base. This pre-confinement and pre-acceleration of electrons in the emitter ensures high current density is achieved independently of base thickness, allowing thin base for high gain without sacrificing current density
3Ease of manufacture
If conventional contact fabrication is used, then manufacturing is simpler, but base access resistance is high
Solution Approach 1:
The patent replaces conventional mechanical/sputtering contact fabrication with atomic layer etching (ALE) process. ALE provides atomic-level precision in creating base contacts, achieving low base access resistance through precise control of contact geometry and interface quality, while remaining manufacturable through standard semiconductor processing
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 design achieves high collector current density and common-emitter gain, surpassing previous nitride-based HET performance, with the use of polarization engineering and atomic layer etching minimizing scattering and enhancing electron injection efficiency.
Implementation Method 1
a triangular quantum well is formed adjacent to the tunneling barrier, and is thermionically filled with electrons
Implementation Method 2
a triangular quantum well is formed by polarization fields at an interface of the emitter stack and the tunneling barrier
Implementation Method 3
The use of only polarization charge in the undoped 10 nm-thick base allowed for high gain, through minimization of scattering
Data Source
AI summary
III-nitride-based hot electron transistors (HETs) offer significant promise as high-speed, high-power devices, but their performance has been limited to below that of competing technologies. A HET with collector current density >440 kA/cm2 and common-emitter current gain >75 is disclosed. Polarization engineering of the emitter stack was used to allow for high-current collimated electron injection from the emitter with relatively low turn-on voltage. The use of only polarization charge in the undoped 10 nm-thick base allowed for high gain, through minimization of scattering, with atomic layer etching contact fabrication used to lower base access resistance.