Vertical Multi-Junction SST Layout for Current Spreading and Heat

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Solution Overview

Problem

Conventional high-voltage LEDs and solid-state transducers (SSTs) face performance limitations due to poor current spreading, thermal characteristics, and low efficiency, particularly in lateral configurations, which necessitate the development of more efficient high-voltage SSTs for improved light extraction and overall performance.

Innovation Solution

The implementation of multi-junction SST devices with buried or vertical contacts, where SST dies are electrically coupled in series, utilizing N-type GaN for enhanced current spreading and incorporating reflective materials to improve light extraction, along with a conductive carrier substrate for thermal management, results in increased efficiency and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional lateral LED configurations are used, then device structure is simple, but current spreading is poor and efficiency is low

Engineering Contradiction:

Improvedevice structure simplicityVSAvoidcurrent spreading and efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent inverts the conventional lateral LED configuration by implementing a vertical LED structure where the light emission direction is perpendicular to the substrate. This inversion allows N-type GaN to be positioned at the front surface, enabling effective current spreading across the active region while maintaining manufacturing feasibility through standard vertical growth processes

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from a two-dimensional lateral current flow in conventional LEDs to a three-dimensional vertical structure with current spreading in the lateral direction enabled by N-type GaN positioning. This dimensional change allows simultaneous achievement of vertical light emission and lateral current distribution

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If conventional LEDs with low forward junction voltage are used, then compatibility with low-voltage power supplies is good, but efficiency when used with high-voltage power supplies is poor

Engineering Contradiction:

Improvepower supply compatibilityVSAvoidsystem efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent modifies the electrical parameters of the LED by using multiple LED dies connected in series configuration, increasing the forward junction voltage from conventional low-voltage levels to high-voltage operation (e.g., 60V or higher). This parameter change enables direct compatibility with high-voltage power supplies and eliminates the need for complex AC/DC rectifiers and DC/DC converters, thereby reducing energy loss in the power supply system

Inventive Principle:

Principle #35Parameter changes

3Power

If high-voltage LEDs are implemented using series-connected lateral dies, then operating voltage increases, but thermal characteristics and current spreading deteriorate

Engineering Contradiction:

Improveoperating voltageVSAvoidthermal characteristics and current spreading

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent inverts the structure by positioning N-type GaN at the front surface of vertical LED dies, allowing inherent current spreading properties of N-type material to be utilized. This structural inversion maintains excellent current spreading and thermal characteristics while achieving high operating voltage through series connection of vertically-oriented dies

Inventive Principle:

Principle #13The other way round (Inversion)

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 enhances current uniformity, light extraction, and overall efficiency of high-voltage SSTs, allowing them to operate effectively with standard AC power supplies and reducing the need for additional drivers, while improving thermal performance and system efficiency.

Implementation Method 1

utilizing N-type GaN for enhanced current spreading

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

incorporating reflective materials to improve light extraction

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

incorporating reflective materials to improve light extraction, along with a conductive carrier substrate for thermal management

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS12155026B2High-voltage solid-state transducers and associated systems and methods

Publication Date: 2024.11.26 MICRON TECHNOLOGY INC

AI summary

High-voltage solid-state transducer (SST) devices and associated systems and methods are disclosed herein. An SST device in accordance with a particular embodiment of the present technology includes a carrier substrate, a first terminal, a second terminal and a plurality of SST dies connected in series between the first and second terminals. The individual SST dies can include a transducer structure having a p-n junction, a first contact and a second contact. The transducer structure forms a boundary between a first region and a second region with the carrier substrate being in the first region. The first and second terminals can be configured to receive an output voltage and each SST die can have a forward junction voltage less than the output voltage.