Gradient Doping in Low Band Gap Semiconductor Devices
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Solution Overview
Problem
Low band gap materials, such as germanium, are susceptible to increased leakage in semiconductor devices, particularly when heavily doped, leading to higher power consumption and potential circuit failure due to tunneling leakage across semiconductor junctions.
Innovation Solution
Gradient doping is implemented to create a transition region in the drain junction with increasing dopant concentrations, pulling back the valence band and increasing the distance for holes to tunnel, thereby reducing off-currents without significantly impacting external resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low band gap materials are used in semiconductor devices, then device performance is improved, but leakage increases due to tunneling across junctions
Solution Approach 1:
The patent applies gradient doping to create a transition region with spatially varying dopant concentrations between the semiconductor region and drain region. This local variation in doping concentration (from lower near the semiconductor region to higher near the drain region) creates a tailored electrical profile that reduces tunneling leakage specifically at the junction interface while preserving the low band gap material's performance benefits in the active channel region.
2Reliability
If heavily doped low band gap materials are used, then conductivity is improved, but tunneling leakage increases exponentially
Solution Approach 1:
The drain junction is segmented into two distinct regions: a semiconductor region with lower dopant concentration and a drain region with higher dopant concentration, separated by a transition region. This segmentation allows the heavily doped region to provide conductivity while the lightly doped semiconductor region and transition region suppress tunneling leakage by creating a more gradual band structure.
Solution Approach 2:
The patent changes the dopant concentration parameter spatially across the drain junction, creating a gradient from lower concentrations near the semiconductor region to higher concentrations near the drain region. This parameter variation optimizes the balance between conductivity (achieved through higher doping) and leakage suppression (achieved through lower doping near the junction interface).
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 effectively lowers the probability of tunneling, resulting in reduced leakage and power consumption while maintaining external resistance, thus enhancing the performance and reliability of low band gap material devices.
Implementation Method 1
Gradient doping is implemented to create a transition region in the drain junction with increasing dopant concentrations, pulling back the valence band and increasing the distance for holes to tunnel
Implementation Method 2
leakage is a quantum phenomenon where mobile charge carriers (electrons or holes) tunnel across a junction or through an insulating region
Data Source
AI summary
An apparatus is provided which comprises: a semiconductor region on a substrate, a gate stack on the semiconductor region, a source region of doped semiconductor material on the substrate adjacent a first side of the semiconductor region, a drain region of doped semiconductor material on the substrate adjacent a second side of the semiconductor region, and a transition region in the drain region, adjacent the semiconductor region, wherein the transition region comprises varying dopant concentrations that increase in a direction away from the semiconductor region. Other embodiments are also disclosed and claimed.