Silicon Light-Emitting Structure With Wedge-Shaped Tip
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Solution Overview
Problem
Silicon-based microelectronic devices have low photon emission efficiency due to their indirect band gap semiconductor material, limiting their effectiveness as sources of electroluminescent radiation, despite efforts to integrate active optical components.
Innovation Solution
A silicon-based high-density array of light-emitting p-n junctions with a wedge-shaped tip is created, where the n-type junction regions are arranged in rows and columns with projections that narrow to points, enhancing the electric field and avalanche current density, thereby increasing luminescence intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reverse biased p-n junction is used to generate light through avalanche breakdown, then photon emission efficiency is improved, but the structure complexity increases due to the need for specific junction geometries and doping profiles
Solution Approach 1:
The patent applies local quality by creating a wedge-shaped tip region in the p-n junction where the doping concentration and geometric shape are specifically tailored to concentrate the electric field. This localized modification at the tip region enhances avalanche breakdown and photon emission efficiency without requiring the entire device structure to be complex, thus resolving the contradiction between improved photon emission and reduced structure complexity.
Solution Approach 2:
The patent employs asymmetry by designing the p-n junction with a wedge-shaped tip rather than a symmetric circular or planar geometry. This asymmetric shape creates a non-uniform electric field distribution that concentrates the field at the tip, enhancing avalanche multiplication and light emission. The asymmetric design achieves higher photon emission efficiency without proportionally increasing overall device complexity.
2Illumination intensity
If a wedge-shaped tip is used to confine the electric field and increase avalanche current density, then luminescence intensity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by forming the wedge-shaped tip structure and doping profile during the initial semiconductor fabrication process using standard photolithography and ion implantation techniques. By pre-establishing the geometric shape and doping concentration gradient before device operation, the design achieves high luminescence intensity while avoiding the need for complex post-fabrication adjustments, thus managing manufacturing precision requirements.
Solution Approach 2:
The patent utilizes parameter changes by varying the doping concentration as a function of depth and lateral position within the wedge-shaped tip region. By controlling the doping profile parameters (concentration, depth, lateral distribution) during fabrication, the design optimizes electric field confinement and avalanche current density to achieve high luminescence intensity with manufacturable precision tolerances.
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 significantly increases light emission by up to four times from a region of a silicon semiconductor, improving photon emission efficiency through the avalanche breakdown mechanism.
Implementation Method 1
Avalanche breakdown occurs when the p-n junction is reverse biased to the point of where the electric field across the junction accelerates electrons into having ionizing collisions with the lattice. The ionizing collisions generate additional electrons which, along with the original electrons, are accelerated into having additional ionizing collisions. As this process continues, the number of electrons increases dramatically in a very short period of time, producing a current multiplication effect.
Data Source
AI summary
A silicon-based light emitting structure is formed as a high density array of light-emitting p-n junctions that substantially increases the intensity of the light emitted in a planar region. The p-n junctions are formed using standard CMOS processing methods, and emit light in response to applied voltages that generate avalanche breakdown and an avalanche current.