HEMT Barrier Layer Impurity Segmentation for Low On-Resistance
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Solution Overview
Problem
High electron mobility transistors (HEMTs) with normally-off characteristics face challenges in achieving stable operation and low on-resistance due to limitations in silicon material efficiency and impurity concentration control, leading to issues with threshold voltage and gate leakage currents.
Innovation Solution
The HEMT design includes a channel layer with barrier layers having a greater energy band gap, a p-type semiconductor layer, and strategically varying impurity concentrations in the barrier layers to control threshold voltage and on-resistance, along with diffusion barrier layers to prevent impurity diffusion, ensuring stable normally-off characteristics and low on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If impurity concentrations in barrier layers are increased to reduce on-resistance, then on-resistance decreases, but threshold voltage control becomes difficult and gate leakage currents increase
Solution Approach 1:
The barrier layer is divided into multiple sub-layers (first barrier layer, second barrier layer, third barrier layer) with different impurity concentration profiles. This segmentation allows each sub-layer to contribute differently to resistance reduction while maintaining overall threshold voltage control, resolving the contradiction between low on-resistance and stable threshold voltage.
Solution Approach 2:
Different regions of the barrier layer are assigned different impurity concentrations tailored to their specific functions. The first barrier layer has higher impurity concentration for resistance reduction, while the second and third barrier layers have lower concentrations for threshold voltage stability. This local differentiation enables simultaneous optimization of both on-resistance and threshold voltage control.
2Reliability
If impurity concentrations are varied to achieve normally-off characteristics, then normally-off characteristics are achieved, but manufacturing precision requirements increase
Solution Approach 1:
Diffusion barrier layers are inserted between the barrier layers and the channel layer/p-type semiconductor layer before final impurity diffusion processes. These preliminary barrier structures prevent unwanted impurity diffusion during subsequent manufacturing steps, making it easier to achieve the required impurity concentration profiles and normally-off characteristics without excessive manufacturing precision requirements.
3Manufacturing precision
If diffusion barrier layers are added to prevent impurity diffusion, then impurity control improves, but device complexity increases
Solution Approach 1:
Diffusion barrier layers are introduced as intermediary structures between the barrier layers and the channel layer/p-type semiconductor layer. These intermediary layers serve as impurity diffusion blockers during manufacturing processes, enabling precise impurity concentration control without requiring extremely complex processing steps. The diffusion barrier layers act as mediators that simplify the overall manufacturing precision requirements.
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 design achieves stable normally-off characteristics and reduced on-resistance by controlling impurity concentrations and preventing impurity diffusion, enhancing the HEMT's operational efficiency and reliability.
Implementation Method 1
An HEMT includes semiconductor layers having different electrical polarization characteristics from each other. In the HEMT, a semiconductor layer having a relatively great polarization rate may cause a two-dimensional electron gas (2DEG) in another semiconductor layer hetero-joined thereto.
Implementation Method 2
In order to implement an HEMT having normally-off characteristics, a gate semiconductor layer forming a depletion region in a channel is employed.
Implementation Method 3
the HEMT may further include a first diffusion barrier layer between the p-type semiconductor layer and the plurality of barrier layers to limit and/or prevent diffusion of impurities
Data Source
AI summary
A high electron mobility transistor (HEMT) includes a channel layer, a plurality of barrier layers, and a p-type semiconductor layer. The barrier layers have an energy band gap greater than that of the channel layer. A gate electrode is arranged on the p-type semiconductor layer. A source electrode and a drain electrode are apart from the p-type semiconductor layer and the gate electrode on the barrier layers. Impurity concentrations of the barrier layers are different from each other in a drift area between the source electrode and the drain electrode.