GaN HEMT GajSi1-jN Protective Layer for Electron Gas Concentration
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Solution Overview
Problem
Existing nitride semiconductor substrates with silicon nitride protective layers fail to sufficiently increase the concentration of two-dimensional electron gas while maintaining mobility in high electron mobility transistors (HEMTs), due to the high insulation properties of these layers.
Innovation Solution
A nitride semiconductor substrate structure comprising a GaN electron transit layer, an InAlGaN electron supply layer, and a GajSi1-jN protective layer, where the GajSi1-jN layer is formed using metal organic chemical vapor deposition with specific source gas supply conditions to enhance electron concentration without lowering mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride (SiN) protective layer is formed on the electron supply layer, then the insulation property is improved, but the concentration of two-dimensional electron gas cannot be sufficiently increased
Solution Approach 1:
The protective film is segmented into a multi-layer structure consisting of a first protective film (higher insulation) and a second protective film (lower insulation, higher conductivity) positioned between the electron supply layer and the first protective film. This segmentation allows the system to simultaneously achieve high insulation where needed and sufficient charge removal capability where required, resolving the contradiction between insulation property and electron gas concentration.
Solution Approach 2:
Different regions of the protective film structure are assigned different insulation properties: the first protective film has higher insulation property for overall protection, while the second protective film has lower insulation property to enable charge removal. This local differentiation of properties allows the system to satisfy both requirements of high insulation and sufficient electron gas concentration in different spatial locations.
2Stability of the object's composition
If a first protective film with certain conductivity is provided to remove charges, then charge distribution is improved, but the concentration of two-dimensional electron gas is not sufficiently increased
Solution Approach 1:
The protective film is constructed as a composite structure with two distinct protective films having different electrical properties. The first protective film provides high insulation for charge containment, while the second protective film provides controlled conductivity for charge removal and electron gas concentration enhancement. This composite approach allows simultaneous achievement of charge distribution stability and high electron gas concentration.
Solution Approach 2:
The electrical parameters (insulation property and conductivity) of the protective film are changed by introducing a second protective film with different properties between the electron supply layer and the first protective film. This parameter modification enables the system to achieve both good charge distribution and sufficiently high electron gas concentration that cannot be achieved with a single protective film.
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
This configuration significantly increases the concentration of two-dimensional electron gas while maintaining mobility, suppressing sheet resistance and improving electric characteristics in HEMTs.
Implementation Method 1
a GajSi1-jN protective layer, where the GajSi1-jN layer is formed using metal organic chemical vapor deposition
Data Source
AI summary
A structure for increasing the concentration of two-dimensional electron gas without lowering mobility is provided. That is, a nitride semiconductor substrate is provided which includes a first layer, a second layer, and a third layer. The first layer has a composition of Ina1Alb1Gac1N (0≤a1≤1, 0≤b1≤1, 0≤c1≤1, a1+b1+c1=1). The second layer is formed on the first layer. The second layer has a composition of Ina2Alb2Gac2N (0≤a2≤1, 0≤b2≤1, 0≤c2≤1, a2+b2+c2=1) and has a band gap different from that of the first layer. The third layer is formed on the second layer and has a composition of AjB1-jN (A is a group 13 element, B is a group 13 element or a group 14 element, A≠B, 0<j<1).