Special Topic on VCSEL Laser Simulation

Abstract: This topic utilizes Nuwa TCAD software to simulate the optoelectronic characteristics of VCSELs, showcasing the construction, physical model settings, and simulation results for high-speed and multi-junction VCSEL device structures. The objective is to enable users to fully understand and master Nuwa TCAD's operation and usage, allowing them to perform various VCSEL simulations and optimization designs using this software.

1. Introduction

VCSEL stands for Vertical Cavity Surface Emitting Laser. Since its conceptualization in 1977 by Kenichi Iga at the Tokyo Institute of Technology, the structure and performance of VCSELs have continuously improved over more than four decades, making them well-known and widely adopted. Compared to edge-emitting lasers, VCSELs emit lasers perpendicular to the active layer and substrate, offering several advantages [1]:

1. High luminous efficiency, low working threshold, low power consumption, and energy-saving;
2. Stable wavelength with minimal temperature drift (temperature drift coefficient of about 0.06nm/°C);
3. Short cavity length with large longitudinal mode spacing, enabling single longitudinal mode output;
4. High beam quality, emitting a circular beam spot, facilitating beam coupling and shaping;
5. Simple fabrication, easy packaging, high yield, and low production cost;
6. Large modulation bandwidth and high modulation frequency, meeting the demands for high-capacity, low-latency data transmission;
7. Can form a two-dimensional array light source, which is conducive to integration;

Consequently, VCSELs are widely applied in optical communications, facial recognition, LiDAR, AR/VR devices, smart cars, and other fields. For instance, 905/940nm VCSEL sources based on multi-junction technology offer high power density suitable for vehicle-mounted LiDAR, achieving long-distance scanning. The 850nm VCSEL source achieves single-channel rates of 10G, 25G, and even 100G, making it ideal for high-speed data communication. Additionally, 905/940nm VCSEL sources are used in consumer electronics for facial recognition, gesture recognition, TOF ranging, and 3D sensing.

However, the rapid development of 5G communication, cloud computing, and military applications has raised the requirements for VCSEL power and data bandwidth. To meet the growing demands, VCSELs require optimized design in material composition and film layer quality, multi-quantum well structure, doping distribution, oxide aperture, and mesa size to improve differential gain, reduce losses, increase modulation bandwidth, and achieve higher power and speed in VCSEL product performance.

Simulation technology, as a low-cost and high-efficiency method for device performance optimization, has been widely applied. To further optimize high-power and high-speed VCSEL devices, this topic focuses specifically on simulating high-speed and multi-junction VCSELs. This includes device structure, model settings, and output of results, showcasing the capabilities and role of simulation technology, enabling users to utilize simulation technology for the optimization and design of VCSEL optoelectronic performance.

2. Simulation Tools

This topic simulates high-speed and multi-junction VCSELs using the Nuwa TCAD semiconductor process and device simulation software. Nuwa TCAD software calculates the longitudinal optical characteristics of VCSELs using the multi-layer film optical transfer matrix method. It employs the effective refractive index method to solve the scalar optical wave equation, calculating the transverse mode characteristics of VCSELs. It considers the coupling of optical, electrical, thermal, mechanical, tunneling, and self-heating models and self-consistently solves the basic semiconductor drift-diffusion equations to achieve a simulation of VCSEL optoelectronic characteristics.