Photodiode Superlattice Intermediate Layer Dark Current Reduction
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Solution Overview
Problem
Infrared image sensors operating at higher temperatures experience increased dark current, which affects their performance, and existing solutions like current blocking layers are not sufficient to mitigate this issue effectively.
Innovation Solution
A photodiode design incorporating a light absorbing layer with a first superlattice structure sensitive to infrared light, an intermediate layer with a conduction band energy level lower than the p-type semiconductor region, and a p-type semiconductor region, which traps electrons and reduces dark current by creating a well potential that prevents electrons from reaching the n-side electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the operating temperature of the infrared image sensor is increased, then the operational versatility and reduced cooling requirements are improved, but the dark current increases and performance deteriorates
Solution Approach 1:
An intermediate layer is introduced between the p-type semiconductor region and the light absorbing layer. This intermediate layer acts as a mediator with a conduction band energy level positioned between the p-type region and the light absorbing layer, creating a potential barrier that blocks electron flow while allowing hole transport, thus reducing dark current at elevated temperatures
2Object-generated harmful factors
If a current blocking layer is added to reduce dark current, then the dark current is reduced, but the device complexity increases
Solution Approach 1:
The intermediate layer utilizes changes in band energy levels (conduction band positioning) to achieve electron blocking. By carefully selecting the conduction band energy level of the intermediate layer to be between the p-type region and light absorbing layer, the structure achieves dark current reduction through parameter optimization rather than complex multi-layer configurations
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 proposed photodiode structure effectively reduces dark current, enabling operation at higher temperatures while maintaining sensitivity, as demonstrated by its performance in temperatures up to 190 Kelvin without the need for extensive cooling.
Implementation Method 1
the intermediate layer having a conduction band having a bottom energy level lower than that of the p-type semiconductor region... traps electrons flowing in the direction from the p-type semiconductor region to the light absorbing layer
Implementation Method 2
a light absorbing layer including a first superlattice structure that includes first semiconductor layers and second semiconductor layers, the first superlattice structure having a band structure sensitive to infrared light
Data Source
AI summary
A photodiode includes a light absorbing layer including a first superlattice structure that includes first semiconductor layers and second semiconductor layers, the first superlattice structure having a band structure sensitive to infrared light; a p-type semiconductor region; and an intermediate layer disposed between the p-type semiconductor region and the light absorbing layer, the intermediate layer having a conduction band having a bottom energy level lower than that of the p-type semiconductor region.