Composite Base Epitaxial Structure for Low-Voltage InGaP HBTs
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Solution Overview
Problem
Conventional indium gallium phosphide (InGaP)-based heterojunction bipolar transistors (HBTs) have high turn-on voltage, leading to increased power consumption and limited application in low power devices, and require improved power-added efficiency for high-frequency applications.
Innovation Solution
An epitaxial structure with a composite base unit comprising a first base layer of InxGa(1-x)AS(1-y)Ny and a second base layer of InmGa(1-m)As, where the emitter unit is made of gallium indium phosphide (GaInP)-based material, reducing the conduction band spike and turn-on voltage, and enhancing carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional InGaP-based HBT is used, then high reliability is achieved, but turn-on voltage becomes high leading to increased power consumption
Solution Approach 1:
The base is segmented into two distinct layers: a first base layer made of InGaAsN material and a second base layer made of InGaAs material. This segmentation allows each layer to perform different functions - the first base layer reduces the conduction band spike to lower turn-on voltage, while the second base layer maintains high carrier mobility and reliability, thus resolving the contradiction between low power consumption and high reliability
Solution Approach 2:
The patent employs composite material structure by combining InGaAsN and InGaAs materials in a layered configuration. The InGaAsN material in the first base layer provides lower bandgap and reduced conduction band offset, while the InGaAs material in the second base layer provides high electron mobility. This composite approach enables simultaneous achievement of low turn-on voltage (reduced power consumption) and high reliability
2Use of energy by moving object
If turn-on voltage is reduced for low power consumption, then power consumption decreases, but frequency properties may deteriorate
Solution Approach 1:
Different regions of the base (first base layer and second base layer) are assigned different material compositions with specific local qualities. The first base layer (InGaAsN) is optimized for reducing conduction band offset and turn-on voltage, while the second base layer (InGaAs) is optimized for high electron mobility and frequency response. This local quality differentiation allows the device to achieve both low power consumption and high frequency properties simultaneously
Solution Approach 2:
The patent changes material composition parameters by introducing nitrogen into the InGaAs material to form InGaAsN in the first base layer. This parameter change (adding nitrogen) modifies the band structure to reduce the conduction band offset, lowering turn-on voltage. Meanwhile, the InGaAs second base layer maintains high electron mobility through appropriate composition control, preserving frequency properties despite the turn-on voltage reduction
Data Source
AI summary
An epitaxial structure includes a composite base unit and an emitter unit. The composite base unit includes a first base layer and a second base layer formed on the first base layer. The first base layer is made of a material of InxGa(1-x)As(1-y)Ny, in which 0<x≤0.2, and 0≤y≤0.035, and when y is not 0, x=3y. The second base layer is made of a material InmGa(1-m)As, in which 0.03≤m≤0.2. The emitter unit is formed on the second base layer 12 opposite to the first base layer 11, and is made of an indium gallium phosphide-based material. A transistor including the epitaxial structure is also disclosed.