GaInNAsSb Base Layer for GaAs HBT Lattice Matching
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Solution Overview
Problem
Semiconductor materials with narrow bandgaps are needed to reduce base resistances, turn-on voltages, and offset voltages in Gallium Arsenide (GaAs) heterojunction bipolar transistors (HBTs) while maintaining adequate lattice matching with the underlying GaAs substrate, as poor lattice matching leads to performance degradation due to lattice stresses.
Innovation Solution
A semiconductor structure is developed using a Gallium Indium Nitride Arsenide Antimonide (GaInNAsSb) compound as the base layer, which has a low bandgap and substantially matches the lattice constant of the GaAs substrate, reducing base resistances and turn-on voltages while maintaining current gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor materials with narrow bandgaps are used to reduce base resistances and turn-on voltages, then electrical performance is improved, but lattice matching with GaAs substrate deteriorates causing performance degradation
Solution Approach 1:
The patent employs a composite material approach by using InGaAs channel layer combined with InAlAs barrier layers to form a heterostructure. This composite structure enables the channel to achieve narrow bandgap properties for low resistance and low turn-on voltage, while the InAlAs barrier layers provide lattice matching compatibility with the GaAs substrate, thus resolving the contradiction between electrical performance improvement and lattice matching requirements
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the composition ratios (indium and gallium content) and thickness parameters of the InGaAs and InAlAs layers. By adjusting these parameters, the channel achieves optimal narrow bandgap characteristics while the barrier layers maintain lattice matching with the substrate, resolving the contradiction through precise parameter optimization
Data Source
AI summary
Embodiments of semiconductor structure are disclosed along with methods of forming the semiconductor structure. In one embodiment, the semiconductor structure includes a semiconductor substrate, a collector layer formed over the semiconductor substrate, a base layer formed over the semiconductor substrate, and an emitter layer formed over the semiconductor substrate. The semiconductor substrate is formed from Gallium Arsenide (GaAs), while the base layer is formed from a Gallium Indium Nitride Arsenide Antimonide (GaInNAsSb) compound. The base layer formed from the GaInNAsSb compound has a low bandgap, but a lattice that substantially matches a lattice constant of the underlying semiconductor substrate formed from GaAs. In this manner, semiconductor devices with lower base resistances, turn-on voltages, and/or offset voltages can be formed using the semiconductor structure.