HgCdTe P-N Diode Heterostructure Self-Positioning
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Solution Overview
Problem
The existing manufacturing process for p/n heterostructure diodes in Hg1-xCdxTe materials faces challenges such as difficulty in growing defect-free surface layers, unpredictable positioning of the p/n junction relative to the heterojunction, and variability in cadmium concentration, leading to inconsistent diode performance and increased noise and dark current.
Innovation Solution
A method involving selective inter-diffusion of cadmium within the p+ doped zone to create a box with a constant cadmium concentration, ensuring the heterojunction is contained within the p+ doped zone and precisely positioned relative to the p/n junction, thereby controlling the diode's performance and reducing variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface layer with higher cadmium concentration is grown over the sole to create a heterostructure, then the diode becomes less sensitive to defects and dark current is reduced, but the positioning of the p/n junction relative to the heterojunction becomes unpredictable and defect-free layer growth becomes difficult
Solution Approach 1:
The p+ doped zone is created in advance before forming the surface layer. This preliminary doping action establishes a predefined region that will later guide the selective inter-diffusion of cadmium, ensuring the heterojunction forms at the correct position relative to the p/n junction without requiring precise control during surface layer growth
Solution Approach 2:
The selective inter-diffusion process uses the p+ doped zone itself as the template for heterojunction formation. The cadmium atoms naturally diffuse into the p+ region during thermal processing, creating the heterostructure automatically positioned relative to the p/n junction without external intervention or complex alignment procedures
2Ease of manufacture
If ion implantation and diffusion methods are used to create the p+ doped zone, then the heterojunction can be formed, but the relative positioning of the p/n junction to the heterojunction varies and reproducibility decreases
Solution Approach 1:
The method combines ion implantation of dopant atoms with subsequent thermal diffusion in a unified process sequence. The dopant atoms are implanted at low energy to create a concentrated p+ zone, then thermal diffusion spreads them to form the heterostructure. This merged approach ensures the heterojunction forms precisely where the p+ zone is located, improving positioning reproducibility
Solution Approach 2:
The process controls the energy and dose parameters of ion implantation to precisely define the p+ doped zone depth and concentration profile. By adjusting these parameters, the heterojunction position can be consistently controlled relative to the p/n junction across multiple diodes, enhancing manufacturing precision
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 results in improved reproducibility and reliability of diode performance by ensuring consistent cadmium concentration and positioning of the heterojunction, minimizing noise and dark current, and enhancing the uniformity of diode characteristics across multiple diodes.
Implementation Method 1
a method involving selective inter-diffusion of cadmium within the p+ doped zone to create a box with a constant cadmium concentration
Implementation Method 2
the interface between the 1.0 n-doped region and the 9.0 p+ doped region is commonly referred to as the 10.0 'p/n junction'. At thermodynamic equilibrium, a space charge zone 7.0 forms on either side of the p/n junction 10.0. In a first limit 7.1 of the space charge zone 7.0, the n-doped sole 1.0 is positively charged and in a second limit 7.2 of the space charge zone, the p+ doped zone 9.0 is negatively charged inducing an electric field intense.
Data Source
Figure 1~2B
Figure 2C~2E
Figure 2F~3
AI summary
The invention relates to a device comprising at least one p-n diode having a heterostructure, including an HgCdTe substrate that comprises, for each diode: a first portion (4) having a first cadmium concentration; a concentrated portion (11) having a second cadmium concentration greater than the first concentration, thereby forming a heterostructure with the first portion (4); and a p+-doped area (9) located in the concentrated portion (11) and extending into the first portion, thereby forming a p-n junction (10) with an n-doped portion of the first portion (4), referred to as a sole plate (1), characterized in that the concentrated portion (11) is located only in the p+-doped area (9) and forms a casing (12) having a given cadmium concentration.