We report new capabilities in our Sentaurus-Device<sup>1</sup> simulator for modeling arbitrarily shaped 2D/3D white
LEDs by coupling novel photon recycling, luminescent spectral conversion effects and electrical transport self
consistently. In our simulator, the spontaneous emission spectra are embedded in ray tracing, and are allowed
to evolve as the rays traverse regions of stimulated gain, absorption, and luminescence. In the active quantum
well (QW), the spontaneous emission spectrum can be partially amplified by stimulated gain within a certain
energy range and absorbed at higher energies, resulting in a modified spontaneous spectrum. The amplified
and absorbed parts of the spectrum give a net recombination/generation rate that is feedback to the electrical
transport via the continuity equations. This conceives a novel photon recycling model that includes amplified
spontaneous emission. The modified spontaneous spectrum can further be altered by spectral conversion in the
luminescent region. In this manner, we capture the important physical effects in white LED structures in a fully
coupled and self-consistent electro-opto-thermal simulation.
This paper illustrates how technology computer-aided design (TCAD), which nowadays is an essential part of CMOS
technology, can be applied to LED development and manufacturing. In the first part, the essential electrical and optical
models inherent to LED modeling are reviewed. The second part of the work describes a methodology to improve the
efficiency of the simulation procedure by using the concept of process compact models (PCMs). The last part
demonstrates the capabilities of PCMs using an example of a blue InGaN LED. In particular, a parameter screening is
performed to find the most important parameters, an optimization task incorporating the robustness of the design is
carried out, and finally the impact of manufacturing tolerances on yield is investigated. It is indicated how the concept
of PCMs can contribute to an efficient design for manufacturing DFM-aware development.
Electrostatic Discharge (ESD) events can cause irreversible damage during production, packaging and application
of Vertical-Cavity Surface Emitting Lasers (VCSELs). Experimental investigation of those damage patterns
inside a real device is a complex and expensive task. Simulation tools can provide insight into the physics during
an actual discharge event. This paper aims to analyze ESD events in VCSELs with a microscopic simulation.
With the help of a state-of-the art Technology Computer Aided Design (TCAD) virtual ESD tests are
performed on oxide-confined VCSELs. The 2-D simulation model takes into account high-field effects and
self-heating in a hydrodynamic framework that allows time-dependent spatially resolved monitoring of critical
quantities (such as electric field across the oxide, temperature profile, current densities) during the ESD events.
Human Body Model (HBM), Machine Model (MM) and Charged Device Model (CDM) show typical local
heating and current crowding effects which may lead to irreversible damaging of the device. For slow ESD events
the temperature peak is found near the center of the device. Faster pulses show maximum temperature at the
interface between oxide and aperture. Physics-based explanations in terms of local electric field, heat generation
and heat transport are given. Oxide aperture, thickness and its position relative to the intrinsic region strongly
influence self-heating, electric fields, current density profiles and the dielectric breakdown conditions. The impact
of those factors on ESD robustness are analyzed and guidelines for robust ESD design in VCSELs are presented.
Yield enhancement and reliability improvement are main requirements in todays industrial VCSEL manufacturing. This requires a thorough understanding of process tolerances and the effects resulting
from design variations. So far, this has been done by statistical
analysis of experimental data. In this work, we use a state-of-the art technology computer aided design (TCAD) tool to analyze device
reliability and yield for multiple VCSEL designs. The starting point is a physics-based simulation model that is calibrated to temperature-dependent static and dynamic measurements for a set of single- and multi-mode VCSELs lasing at 850 nm. Applying statistical variations that result from design modifications and process fluctuations, yield and reliability data are extracted by means of simulation. The yield will be derived by compliance to selected device specifications (such available single-mode power), and the device reliability is determined from an analysis of the internal device properties. As example, the oxide aperture and metal aperture design will be discussed, and a robust design will be presented.