Epitaxial Wafer with Low-Impurity Quantum Well for Photodiodes
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Solution Overview
Problem
Existing photodiodes in the near-infrared to infrared region suffer from high dark current due to high carrier concentration in the absorption layer, which reduces sensitivity and image quality, especially when extending detection wavelength to longer regions.
Innovation Solution
A photodiode with a III-V semiconductor substrate and a multiple quantum well structure is developed, where the total concentration of impurities is limited to less than or equal to 5×10^15 cm^-3, specifically controlling sulfur, selenium, tellurium, silicon, germanium, and tin concentrations to minimize dark current and maintain sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the carrier concentration of the absorption layer is increased, then the sensitivity is improved, but the dark current increases
Solution Approach 1:
The invention changes the parameter of carrier concentration in the absorption layer by reducing it to less than 1×10^16 cm^-3, which simultaneously suppresses dark current while maintaining sensitivity through the optimized multiple quantum well structure
Solution Approach 2:
The invention uses a composite multiple quantum well structure with specific material composition (InGaAs/GaAsSb type-II MQW) that enables efficient light absorption while maintaining low carrier concentration, thus resolving the contradiction between sensitivity and dark current
2Object-generated harmful factors
If the carrier concentration of the absorption layer is reduced, then the dark current is suppressed, but the sensitivity deteriorates
Solution Approach 1:
The multiple quantum well structure with optimized material composition compensates for the reduced carrier concentration, maintaining high sensitivity through enhanced light absorption efficiency in the low-carrier-concentration regime
Solution Approach 2:
The invention optimizes multiple parameters including well width, barrier width, and material composition ratios to achieve high sensitivity at low carrier concentration, transforming the trade-off into a synergistic design space
3Adaptability or versatility
If semiconductor layers containing antimony are grown to extend detection wavelength, then the detection wavelength is extended, but it becomes difficult to obtain absorption layers with low carrier concentration
Solution Approach 1:
The invention changes the growth parameters and source material purity requirements to achieve low carrier concentration in antimony-containing layers, enabling wavelength extension without sacrificing carrier concentration control
Solution Approach 2:
The invention introduces an intermediary layer or interface structure that facilitates the growth of low-carrier-concentration antimony-containing semiconductor layers, acting as a mediator between the substrate and the active absorption layer
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
The approach effectively suppresses dark current and ensures good sensitivity by reducing impurity concentrations, thereby improving image quality and extending detection wavelength without degrading crystal structure.
Implementation Method 1
an absorption layer having a bandgap energy corresponding to light in a near-infrared to infrared region
Data Source
AI summary
An epitaxial wafer which allows manufacture of a photodiode having suppressed dark current and ensured sensitivity, and a method for manufacturing the epitaxial wafer, are provided. The epitaxial wafer of the present invention includes: a III-V semiconductor substrate; and a multiple quantum well structure disposed on the substrate, and including a plurality of pairs of a first layer and a second layer. The total concentration of elements contained as impurities in the multiple quantum well structure is less than or equal to 5×1015 cm−3.