Nitride Semiconductor Device Leakage Current Reduction
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Solution Overview
Problem
Conventional nitride semiconductor devices, such as Schottky diodes, experience significant backward leakage current, particularly at high operating voltages, which is not adequately addressed by existing methods that reduce leakage current only at low voltages.
Innovation Solution
A nitride semiconductor device structure is implemented with a laminated body of AlGaN/GaN layers, a channel layer with varying carrier concentrations, and a p-AlGaN block layer inserted between electrodes, which reduces on-resistance and backward leakage current by controlling carrier concentrations and increasing the film thickness of the uppermost AlGaN barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Schottky diode structure is used with undoped AlGaN/GaN heterostructure, then high current density and low forward threshold voltage are achieved, but large backward leakage current occurs
Solution Approach 1:
The device is divided into multiple quantum well structures (first and second quantum wells) with different band gaps arranged in sequence, creating multiple channels with different carrier concentrations. This segmentation allows the device to achieve high current density through multiple conduction paths while reducing backward leakage current by having some channels with lower carrier concentrations that suppress leakage.
Solution Approach 2:
Different regions of the device are designed with different local properties: the first quantum well has higher carrier concentration for low resistance, while the second quantum well has lower carrier concentration for leakage suppression. This local quality differentiation allows simultaneous optimization of both current density and leakage current characteristics.
2Object-generated harmful factors
If a p-GaN layer is inserted into the anode electrode to reduce interface leakage current, then leakage current is reduced at low operating voltage, but sufficient leakage reduction is not achieved at high operating voltage
Solution Approach 1:
The solution moves from a single-layer approach to a multi-layer quantum well structure with vertical dimensionality. By creating multiple quantum wells at different depths with different band gap configurations, the device addresses leakage current suppression in the vertical dimension, enabling effective leakage reduction across both low and high voltage operating conditions.
Solution Approach 2:
The device employs a composite structure combining AlGaN and GaN layers with different compositions and thicknesses to form quantum wells. This composite material structure creates multiple channels with tailored carrier concentrations, providing both low-voltage and high-voltage leakage current suppression capabilities that a single material layer cannot achieve.
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 effectively reduces both on-resistance and backward leakage current, even at high voltage regions, by lowering the carrier concentration of the uppermost channel layer and increasing the film thickness of the AlGaN barrier layer, thereby improving the device's operational efficiency.
Implementation Method 1
charges are generated at a heterointerface as a result of spontaneous polarization and piezoelectric polarization on (0001) plane
Implementation Method 2
charges are generated at a heterointerface as a result of spontaneous polarization and piezoelectric polarization on (0001) plane
Implementation Method 3
a sheet carrier concentration of 1×10^13 cm^-2 or higher is obtained even in an undoped state. Accordingly, such diode and hetero-junction field effect transistor (HFET) which have higher current density are producible by use of two-dimensional electron gas (2DEG) at a heterointerface
Data Source
AI summary
A nitride semiconductor device includes: a substrate; a buffer layer formed on the substrate; a laminated body formed by two or more cycles of semiconductor layers each including a first nitride semiconductor layer, and a second nitride semiconductor layer having a larger band gap than a band gap of the first nitride semiconductor layer, the first and second nitride semiconductor layers being laminated in this order on the buffer layer; a first electrode; and a second electrode. A channel layer is formed in each of the semiconductor layers at an interface between the first nitride semiconductor layer and the second nitride semiconductor layer. A carrier concentration of the channel layer in the uppermost semiconductor layer is lower than a carrier concentration of each of the channel layers of the other semiconductor layers.