Infrared Detector Pixel Separation Wall Oxidation Prevention
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Solution Overview
Problem
Infrared detectors with type-II superlattice (T2SL) structures on gallium antimonide (GaSb) substrates face increased dark current due to oxidation at pixel separation grooves, leading to reduced signal-to-noise (S/N) ratios.
Innovation Solution
The implementation of a pixel separation wall with a trapezoid shape and inclined side surfaces, formed using compound semiconductors, surrounds each pixel, preventing exposure of the T2SL layers to the atmosphere and thus minimizing oxidation, and a buffer layer is used to create a p-n junction for insulation between pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pixel separation groove is formed to separate pixels, then electrical separation of pixels is achieved, but the end surface of GaSb layer is exposed to atmosphere causing oxidation and increased dark current
Solution Approach 1:
A pixel separation wall made of compound semiconductor material is introduced as an intermediary structure between adjacent pixels. This wall physically separates the pixels electrically while preventing direct exposure of the GaSb layer to the atmosphere, thus eliminating oxidation at the separation region.
Solution Approach 2:
The solution transitions from a planar pixel separation groove (2D surface feature) to a three-dimensional pixel separation wall structure. The wall extends vertically to cover the end surface of the GaSb layer, adding a vertical dimension to the separation mechanism and simultaneously providing atmospheric protection.
2Ease of manufacture
If the end surface of GaSb layer is exposed to atmosphere, then pixel separation is simplified, but oxidation occurs forming interface states that increase dark current
Solution Approach 1:
The pixel separation wall is formed before subsequent processing steps, preliminarily protecting the GaSb layer end surface from atmospheric exposure. This preliminary protective action prevents oxidation before it can occur, maintaining low dark current levels throughout the manufacturing process.
Solution Approach 2:
The pixel separation wall creates a physical barrier that effectively establishes an inert environment around the GaSb layer end surface, preventing atmospheric oxygen from reaching and oxidizing the semiconductor material, thus maintaining electrical performance.
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
This design effectively reduces dark current and maintains a high S/N ratio by preventing oxidation of the T2SL layers, enhancing the performance of infrared detectors with T2SL structures.
Implementation Method 1
GaSb having a T2SL structure formed therein is likely to be oxidized. When a pixel separation groove is formed and the end surface of a GaSb layer is thus exposed, this portion is exposed to the atmosphere to be oxidized.
Implementation Method 2
a buffer layer formed of the compound semiconductor of the first conductivity type on the first contact layer and a side surface of the pixel separation wall in a region surrounded by the pixel separation wall
Data Source
AI summary
An infrared detector includes a pixel separation wall. The infrared detector includes a semiconductor crystal substrate; a first contact layer formed on the semiconductor crystal substrate, a pixel separation wall formed on the first contact layer and configured to separate pixels; a buffer layer formed on the first contact layer and on a side surface of the pixel separation wall in a region surrounded by the pixel separation wall, an infrared-absorbing layer formed on the buffer layer, a second contact layer formed on the infrared-absorbing layer, an upper electrode formed on the second contact layer, and a lower electrode formed on the first contact layer. The buffer layer and the first contact layer are formed of a compound semiconductor of a first conductivity type. The pixel separation wall and the second contact layer are formed of a compound semiconductor of a second conductivity type.