InAs/GaSb Photodiode Beryllium Doping for Dark Current Reduction
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Solution Overview
Problem
The performance of InAs/GaSb superlattice photodiodes is limited by defect-assisted tunneling when operating at low temperatures, particularly at 77 K, which affects their electrical and optical quality due to the broken-gap type II configuration and spatial separation of electrons and holes.
Innovation Solution
Doping the π-region of the active layer with Beryllium (Be) in long wavelength photodiodes switches the background from n-type to p-type, increasing quantum efficiency and minimizing dark current, thereby enhancing the R0A product and zero-bias differential resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the photodiode operates at low temperatures (77 K), then the dark current is reduced, but the performance is limited by defect-assisted tunneling
Solution Approach 1:
The patent changes the doping parameter from n-type to p-type by introducing Beryllium dopants. This parameter change modifies the background carrier type, which suppresses defect-assisted tunneling mechanisms that limit performance at low temperatures, while maintaining low dark current operation
Solution Approach 2:
Beryllium atoms are introduced as intermediary dopant elements that mediate the electrical properties of the photodiode. The Beryllium doping creates p-type characteristics that act as an intermediary mechanism to suppress defect-assisted tunneling without directly affecting the low temperature operation benefits
2Device complexity
If the background is n-type, then the device structure is simple, but the quantum efficiency is reduced
Solution Approach 1:
The patent changes the fundamental parameter of background doping type from n-type to p-type through Beryllium incorporation. This parameter change directly improves quantum efficiency by optimizing carrier generation and collection mechanisms, despite requiring additional doping process complexity
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 approach leads to improved quantum efficiency, increased zero-bias differential resistance from less than 4 Ω·cm² to 32 Ω·cm² for a 100% cutoff of 12.05 μm, reducing dark current and optimizing the performance of InAs/GaSb superlattice photodiodes at 77 K.
Implementation Method 1
Doping the π-region of the active layer with Beryllium (Be) switches the background from n-type to p-type
Implementation Method 2
electrons can easily tunnel from the conduction band of one layer to the valence band of the other layer (i.e. Zener tunneling)
Implementation Method 3
A type II InAs/GaSb superlattice system is a particularly attractive quantum system because of its flexibility in designing the interband transitions over a wide range of wavelengths
Data Source
AI summary
An improved photodiode and method of producing an improved photodiode comprising doping an InAs layer of an InAs/GaSb region situated on top of an InAs/GaSb:Be superlattice and below an InAs:Si/GaSb regions such that the quantum efficiency of the photodiode increases and dominant dark current mechanisms change from diffusion to band-to-band tunneling as the InAs layer is doped with Beryllium.