VCSEL Tunnel Junction Layout for Low-Loss DBR Resonators
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Solution Overview
Problem
Existing Vertical Cavity Surface Emitting Laser (VCSEL) devices face challenges with optical absorption and electrical losses due to the integration of tunnel junctions, particularly in applications requiring high current pulses and complex electrical driver modulation, such as time-of-flight LIDAR systems.
Innovation Solution
The integration of a tunnel junction between the first and second distributed Bragg reflectors, with specific thickness and conductivity type configurations, reduces optical absorption and electrical losses by optimizing the position within the DBR to minimize current density and absorption, allowing for efficient laser emission and reduced voltage modulation requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a tunnel junction is integrated into the VCSEL device, then electrical losses are reduced, but optical absorption increases
Solution Approach 1:
The patent applies local quality by creating distinct regions within the DBR structure: a first part with high doping concentration (1e19 to 1e21 atoms/cm³) and a second part with lower doping concentration (1e17 to 1e19 atoms/cm³). This spatial variation in doping concentration allows the high-doped region to provide low electrical resistance while the low-doped region maintains low optical absorption, resolving the contradiction between reducing electrical losses and minimizing optical absorption.
2Reliability
If the tunnel junction is positioned closer to the active layer, then electrical performance improves, but optical absorption increases
Solution Approach 1:
The patent positions the tunnel junction within the DBR at a specific location where the standing wave intensity is minimal, and implements local quality variation through different doping concentrations in different regions of the DBR. The first part with higher doping is positioned to optimize electrical contact and current injection, while the second part with lower doping is positioned to minimize optical absorption, achieving both electrical performance and low optical loss.
3Loss of energy
If high doping concentration is used in the tunnel junction, then electrical resistance decreases, but optical absorption increases
Solution Approach 1:
The patent directly applies local quality by dividing the DBR into two parts with different doping concentrations. The first part has high doping concentration (1e19 to 1e21 atoms/cm³) to provide low electrical resistance for efficient current injection, while the second part has lower doping concentration (1e17 to 1e19 atoms/cm³) to minimize optical absorption. This spatial differentiation of material properties resolves the contradiction between electrical and optical performance requirements.
Solution Approach 2:
The patent segments the DBR structure into a first part and a second part with distinct doping concentrations. This segmentation allows each part to be optimized for its specific function: the first part for electrical performance and the second part for optical performance, thereby resolving the contradiction between reducing electrical resistance and minimizing optical absorption.
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 reduces optical absorption by up to a factor of 5 and minimizes electrical losses, enabling efficient operation of VCSEL devices in applications like time-of-flight sensors and LIDAR systems with improved performance and reduced power consumption.
Implementation Method 1
complex simulations have shown that integration of the tunnel junction in one of the DBRs can reduce optical absorption up to a factor of 5
Implementation Method 2
an optical resonator comprising a first distributed Bragg reflector (DBR), a second DBR and an active layer for light emission
Implementation Method 3
an active layer for light emission arranged between the first DBR and the second DBR
Implementation Method 4
A tunnel junction is arranged between the first part and the second part. The first electrical contact and the second electrical contact are arranged to electrically pump the optical resonator such that the tunnel junction is reversely biased during operation of the VCSEL device
Data Source
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AI summary
The invention describes a Vertical Cavity Surface Emitting Laser (VCSEL) device (100). The VCSEL device (100) comprises a first electrical contact (105), a second electrical contact (150) and an optical resonator. The optical resonator comprises a first distributed Bragg reflector (115), a second distributed Bragg reflector (125) and an active layer (120) for light emission. The active layer (120) is arranged between the first distributed Bragg reflector (115) and the second distributed Bragg reflector (125). Either the first distributed Bragg reflector (115) or the second distributed Bragg reflector (125) comprises a first part (115-1, 125-1) with at least one pair of layers with different refractive indices and a second part (115-2, 125-2) with at least one pair of layers with different refractive indices. The first part (115-1, 125-1) and the second part (115-2, 125-2) are characterized by different conductivity types. A tunnel junction (130) is arranged between the first part (115-1, 125-1) and the second part (115-2, 125-2). The first electrical contact (105) and the second electrical contact (150) are arranged to electrically pump the optical resonator such that the tunnel junction (130) is reversely biased during operation of the VCSEL device (100). The tunnel junction is arranged in an optimized position in the first or second distributed Bragg reflector. The invention further relates an optical sensor and a time-of-flight sensor module (200) comprising such a VCSEL device (100). The invention finally relates to a corresponding method of fabricating such a VCSEL device.