GaN Vertical Transistor Barrier Layer Hydrogen Passivation

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Solution Overview

Problem

Vertical GaN-based semiconductor devices face challenges in reducing drain leak current while maintaining high vertical breakdown voltage and low on-resistance, primarily due to the unique structure with an opening that leads to damaged surfaces and enriched conductive impurities.

Innovation Solution

A GaN-based semiconductor device with a specific concentration ratio of hydrogen to impurity in the second conductivity-type barrier layer, which terminates dangling bonds and passivates conductive impurities, reducing drain leak current while maintaining good breakdown voltage characteristics, is developed. The device includes a GaN-based stacked layer with a regrown channel layer and carrier supply layer, covered by an insulating layer, and electrodes, where the hydrogen concentration is optimized to satisfy certain ranges to achieve these results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an opening is formed in the GaN-based semiconductor to increase mobility and decrease on-resistance, then high mobility and low on-resistance are achieved, but drain leak current increases due to damaged surfaces and enriched conductive impurities

Engineering Contradiction:

Improvedrain leak currentVSAvoidconductive impurities enrichment

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of ion irradiation during RIE etching into a beneficial effect by controlling the plasma conditions to simultaneously generate hydrogen atoms that passivate the damaged surfaces and reduce conductive impurities. The harmful ion damage is transformed into an opportunity for surface passivation through carefully controlled plasma chemistry.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the plasma parameters (power, pressure, gas composition) during the RIE process to optimize the balance between etching efficiency and surface damage control. By adjusting these parameters, the plasma environment is controlled to minimize ion damage while maximizing hydrogen-mediated passivation effects.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If RIE or similar methods are used to form the opening, then the opening can be precisely formed, but the end portion of the GaN-based stacked layer is damaged due to ion irradiation and dangling bonds are formed

Engineering Contradiction:

Improveopening formation precisionVSAvoidsurface damage and dangling bonds

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces hydrogen atoms as an intermediary substance during the RIE process. These hydrogen atoms act as a mediator that passivates the damaged surfaces created by ion irradiation, converting the harmful ion-surface interaction into a beneficial hydrogen-passivation effect that reduces dangling bonds and conductive impurities.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The optimized hydrogen concentration in the barrier layer effectively reduces drain leak current and enhances breakdown voltage characteristics, enabling stable high-current switching with low on-resistance in vertical GaN-based semiconductor devices.

Implementation Method 1

hydrogen is distributed in a high concentration so that the above range is satisfied. Therefore, the dangling bonds and the like are terminated and the enriched region of conductive impurities is passivated.

Methodology Applied

Scientific EffectPassivation:

Implementation Method 2

forming a regrown layer including a channel of two-dimensional electron gas (2DEG) on the side surface of the opening

Methodology Applied

Scientific EffectTwo-dimensional electron gas formation:

Data Source

PatentUS8981428B2Semiconductor device including GaN-based compound semiconductor stacked layer and method for producing the same

Publication Date: 2015.03.17 SUMITOMO ELECTRIC INDUSTRIES LTD

AI summary

There are provided a semiconductor device in which a drain leak current can be reduced in the transistor operation while high vertical breakdown voltage is achieved and a method for producing the semiconductor device. In the semiconductor device, an opening 28 that extends from an n+-type contact layer 8 and reaches an n-type drift layer 4 through a p-type barrier layer 6 is formed. The semiconductor device includes a regrown layer 27 located so as to cover portions of the p-type barrier layer 6 and the like that are exposed to the opening, the regrown layer 27 including an undoped GaN channel layer 22 and a carrier supply layer 26; an insulating layer 9 located so as to cover the regrown layer 27; and a gate electrode G located on the insulating layer 9. In the p-type barrier layer, the Mg concentration A (cm−3)and the hydrogen concentration B (cm−3) satisfy 0.1<B/A<0.9 . . . (1).