Small Anode Germanium Well Detector Reducing Capacitance
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Solution Overview
Problem
Conventional germanium well detectors suffer from high capacitance, increased electronic noise, and decreased performance with larger well diameters, limiting their effectiveness in radiation detection, especially at low energies and for small samples.
Innovation Solution
The SAGe well radiation detector system modifies the conventional Ge well structure by placing the P+ contact on the base of the P-type bulk substrate outside the well, reducing capacitance and noise, and allowing for larger well diameters while maintaining better energy resolution than conventional well detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the well diameter is increased to accommodate larger samples, then the detection capability for small samples is improved, but the capacitance increases and energy resolution deteriorates
Solution Approach 1:
The P+ contact is extracted from the well interior and relocated to the base of the detector outside the well. This removes the source of high capacitance from the well structure, allowing the well diameter to be increased for better sample accommodation without the penalty of increased capacitance and degraded energy resolution.
Solution Approach 2:
The P+ contact is moved from a two-dimensional surface contact within the well to a three-dimensional position at the base of the detector. This spatial reconfiguration reduces the capacitance between the P+ and N- contacts while maintaining effective charge collection, enabling larger well diameters without performance loss.
2Productivity
If the P+ contact is placed within the well to maximize charge collection, then the detection efficiency is improved, but the capacitance and electronic noise increase
Solution Approach 1:
The P+ contact is extracted from the well interior where it created high capacitance and electronic noise, and relocated to the base of the detector. This eliminates the harmful electrical effects while preserving the detection efficiency through alternative charge collection geometry.
Solution Approach 2:
The base region of the detector serves as an intermediary structure that allows the P+ contact to be positioned outside the well while maintaining effective charge collection. This intermediary location provides electrical connection without the capacitive coupling problems of interior well placement.
3Volume of moving object
If the conventional well structure is used with large diameter, then the sample accommodation capacity is improved, but the performance characteristics deteriorate
Solution Approach 1:
The P+ contact is removed from the well structure and relocated to the base, decoupling the well diameter from the capacitance determination. This allows the well volume to be increased for better sample accommodation while maintaining stable performance characteristics independent of well diameter.
Solution Approach 2:
The electrical configuration parameter is changed by moving the P+ contact location, which fundamentally alters the capacitance relationship. This parameter change enables the well diameter to be varied for sample accommodation without affecting performance characteristics, achieving independence between geometric and electrical parameters.
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 configuration results in a detector with low capacitance, reduced noise, and improved performance independent of well diameter, enabling better detection of radiation sources and their directionality.
Implementation Method 1
When photons interact with the material within the depleted volume of a detector, charge carriers (holes and electrons) are produced and are swept by the electric field to the P and N electrodes. This charge, which is in proportion to the energy deposited in the detector by the incoming photon, is converted into a voltage pulse
Implementation Method 2
Because germanium has relatively low band gap, these detectors must be cooled in order to reduce the thermal generation of charge carriers (thus reverse leakage current) to an acceptable level. Otherwise, leakage current induced noise destroys the energy resolution of the germanium detector. Typically the detectors are operated at temperatures between 77° K and 120° K
Data Source
AI summary
A small anode germanium well (SAGe well) radiation detector system/method providing for low capacitance, short signal leads, small area bottom-oriented signal contacts, enhanced performance independent of well diameter, and ability to determine radiation directionality is disclosed. The system incorporates a P-type bulk germanium volume (PGEV) having an internal well cavity void (IWCV). The external PGEV and IWCV surfaces incorporate an N+ electrode except for the PGEV external base region (EBR) in which a P+ contact electrode is fabricated within an isolation region. The PGEV structure is further encapsulated to permit operation at cryogenic temperatures. Electrical connection to the SAGe well is accomplished by bonding or mechanical contacting to the P+ contact electrode and the N+ electrode. The EBR of the PGEV may incorporate an integrated preamplifier inside the vacuum housing to minimize the noise and gain change due to ambient temperature variation.