Monolithic HEMT Bias Circuit for Stable Idle Current
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Solution Overview
Problem
In amplifier circuits using high-electron-mobility transistors with nitride semiconductors, manufacturing variations in threshold voltage lead to inconsistent idle current, making it difficult to maintain a desired performance as the idle current affects power gain, distortion, and efficiency, requiring individual adjustments of gate voltages.
Innovation Solution
A monolithic semiconductor device and hybrid semiconductor device are designed with a first nitride semiconductor layer and a second nitride semiconductor layer having a larger band gap, along with a bias circuit that includes a second transistor outside the radio-frequency signal path to apply bias voltage to the gate of the first transistor, reducing the workload for adjusting gate voltages individually.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate voltages are adjusted individually to maintain idle current within acceptable range, then performance consistency is improved, but device complexity and adjustment workload increase
Solution Approach 1:
The patent merges multiple transistors into a single integrated device structure where transistors share common layers and substrates. This integration allows uniform manufacturing conditions to be applied across all transistors, reducing individual variations in threshold voltage and idle current without requiring separate adjustments for each transistor.
Solution Approach 2:
The patent creates a universal transistor design where all transistors in the device use identical layer structures, materials, and manufacturing processes. This universality ensures that all transistors have consistent characteristics, allowing a single gate voltage setting to work for all transistors rather than requiring individual adjustments.
2Ease of manufacture
If manufacturing processes are simplified, then ease of manufacture is improved, but manufacturing precision of threshold voltage decreases
Solution Approach 1:
The patent carefully controls and standardizes key manufacturing parameters such as layer thicknesses, composition ratios, and deposition conditions. By optimizing these parameters within specific ranges, the patent achieves consistent threshold voltages across all transistors while maintaining a relatively simple manufacturing process that can be implemented using standard semiconductor fabrication techniques.
Data Source
AI summary
A monolithic semiconductor device includes: a substrate; a first nitride semiconductor layer disposed on the substrate; a second nitride semiconductor layer disposed on the first nitride semiconductor layer and having a band gap larger than a band gap of the first nitride semiconductor layer; a first transistor disposed on the substrate and including the first nitride semiconductor layer and the second nitride semiconductor layer, the first transistor being of a high-electron-mobility transistor (HEMT) type for power amplification; and a first bias circuit disposed on the substrate and including a second transistor of the HEMT type disposed outside a propagation path of a radio-frequency signal inputted to the first transistor, the first bias circuit applying bias voltage to a gate of the first transistor.