Aluminum gallium nitride/gallium nitride high electron mobility transistors

Abstract

Structures, devices and methods are provided for creating enhanced back barriers that improve the off-state breakdown and blocking characteristics in aluminum gallium nitride AlGaN / GaN high electron mobility transistors (HEMTs). In one aspect, selective fluorine ion implantation is employed when developing HEMTs to create the enhanced back barrier structures. By creating higher energy barriers at the back of the two-dimensional electron gas channel in the unintentionally doped GaN buffer, higher off-state breakdown voltage is advantageously provided and blocking capability is enhanced, while allowing for convenient and cost-effective post-epitaxial growth fabrication. Further non-limiting embodiments are provided that illustrate the advantages and flexibility of the disclosed structures.

Description

technical field [0001] The invention belongs to field effect transistors, and particularly relates to improving the breakdown voltage of AlGaN / GaN high-mobility transistors and related materials, device structures and methods by using fluorine ion implantation. Background technique [0002] High Electron Mobility Transistor (HEMT), also known as Heterojunction Field Effect Transistor (HFET) or Modulation Doped Field Effect Transistor (MODFET), generally utilizes a junction formed by two materials with different band gaps, such as a heterojunction The replacement doped region acts as a channel. High electron mobility transistors benefit from heterostructures, taking advantage of the high-mobility electrons generated by heterojunctions made of, for example, highly doped wide-bandgap n-type donor layers or unintentionally doped AlGaN wide-bandgap layers and an undoped narrow bandgap layer (eg, a GaN layer) with little or no intentional dopant. [0003] For example, since a he...

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Problems solved by technology

Therefore, under high drain bias, electrons may be injected from the source to the high-field region through the GaN buffer layer, causing impact ionization in the channel, leading to three-terminal breakdown before the gate breakdown of the device

[0007] Although attempts have been made to reduce the n-type background doping in GaN buffer layers, such efforts have generally proven difficult and commercially unproductive

In addition, for example, carbon or Fe is doped into the GaN layer to form deep acceptor levels, but these acceptor levels are likely to cause the current collapse of the device and the hysteresis of the current-voltage (I-V) output characteristics, and the intentional introduction of impurities may also lead to Permanent contamination of the growing system

In addition, these acceptor impurities may also lead to device instability, especially when the drain operating voltage is high

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