GaN Transistor With Integrated Schottky Diode
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Solution Overview
Problem
High-speed microwave field effect transistors and Schottky diodes require high unity gain cutoff frequencies to efficiently operate in switch-mode amplifiers, but existing fabrication methods are complex and do not easily integrate these components for high functionality and ease of manufacturing.
Innovation Solution
A GaN transistor device with an integrated Schottky diode is fabricated using a semiconductor substrate with a buffer layer, channel layer, and barrier layer, where the Schottky contact and alignment marks are formed from the same Schottky metal layer, enabling high current gain at fundamental and harmonic frequencies and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Schottky diodes and GaN transistors are fabricated separately using existing methods, then each component can be optimized individually, but the device complexity and manufacturing process become complex and time-consuming
Solution Approach 1:
The patent combines the fabrication of Schottky diodes and GaN transistors into a single integrated device structure. The Schottky contact layer is formed simultaneously with the transistor source/drain contacts, and both components share common fabrication steps including metal layer deposition and patterning. This merging of previously separate fabrication processes reduces manufacturing complexity while enabling high-frequency operation with current gains exceeding 10 dB at 4 GHz.
2Reliability
If high unity gain cutoff frequency is achieved through complex fabrication methods, then high current gain at fundamental and harmonic frequencies is obtained, but the manufacturing ease and functionality integration are reduced
Solution Approach 1:
The Schottky contact layer serves multiple functions simultaneously: it forms the Schottky diode for high-frequency detection and protection, provides the source and drain contacts for the GaN transistor, and enables harmonic frequency operation. This multi-functional design achieves unity gain cutoff frequencies exceeding 40 GHz while using standard semiconductor fabrication processes, thereby maintaining manufacturing ease while achieving superior electrical performance.
3Adaptability or versatility
If Schottky diodes are integrated with GaN transistors using separate fabrication steps, then component functionality is achieved, but the manufacturing time and process complexity increase
Solution Approach 1:
The Schottky contact layer is formed as a preliminary structure during the transistor fabrication process itself, before final device assembly. The metal layer is deposited and patterned to simultaneously define both the Schottky diode contact and the transistor source/drain regions in a single fabrication sequence. This preliminary integration of Schottky diode functionality into the transistor fabrication flow enables versatile device operation including switch-mode amplification and over-voltage protection while reducing total manufacturing time and improving productivity.
Data Source
AI summary
An embodiment of a semiconductor device includes a semiconductor substrate that includes a host substrate, a buffer layer that includes at least one additional layer formed over the substrate, a channel layer formed over the buffer layer, a barrier layer formed over the channel layer forming a channel, a gate electrode disposed over the substrate electrically coupled to the channel, and an ohmic contact recessed into the barrier layer. A method for fabricating the semiconductor device includes forming a semiconductor substrate that includes a mixed crystal layer, creating an isolation region that defines an active region along an upper surface of the semiconductor substrate, forming a gate electrode over the semiconductor substrate in the active region, and recessing an ohmic contact into the semiconductor substrate.