Reliability issues of Gallium Nitride High Electron Mobility Transistors

Abstract

In the present paper we review the most recent degradation modes and mechanisms recently observed in AlGaN/GaN (Aluminum Gallium Nitride/Gallium Nitride). High Electron-Mobility Transistors (HEMTs), as resulting from a detailed accelerated testing campaign, based on reverse bias tests and DC accelerated life tests at various temperatures. Despite the large efforts spent in the last few years, and the progress in mean time to failure values, reliability of GaN HEMTs, and millimeter microwave integrated circuits still represent a relevant issue for the market penetration of these devices. The role of temperature in promoting GaN HEMT failure is controversial, and the accelerating degradation factors are largely unknown. The present paper proposes a methodology for the analysis of failure modes and mechanisms of GaN HEMTs, based on (i) DC and RF stress tests accompanied by an (ii) extensive characterization of traps using deep level transient spectroscopy and pulsed measurements, (iii) detailed analysis of electrical characteristics, and (iv) comparison with two-dimensional device simulations. Results of failure analysis using various microscopy and spectroscopy techniques are presented and failure mechanisms observed at the high electric field values typical of the operation of these devices are reviewed

Time evolution of electrical degradation under high-voltage stress in GaN high electron mobility transistors

“…The activation energy for permanent I Dmax degradation is very close to that of I Dlin and that extracted from long-term life test data in similar devices (E a =1.05 eV) [13]. Also, a similar activation energy was reported for degradation in the DC value of drain current (E a =1.13 eV) under the stress condition of V DS =40 V and I D =200 mA/mm in different devices by a separate team [3].…”

“…To address reliability issues, it is critical to develop detailed physical understanding of the mechanisms behind device degradation. High-voltage stress has been found to result in device degradation with a critical voltage behavior [1][2] and characterized by trap formation and trapping [3][4]. To date, few studies have investigated the time evolution of degradation under high-voltage stress conditions [3,[5][6][7][8].…”

“…Some of these studies focused on the evolution of the gate/drain leakage current [6,8]. Although there have been efforts to understand the time evolution of the drain current [3], its detailed nature is still largely unknown. This is important in order to develop degradation models that can predict device lifetime under given operational conditions.…”

(Invited) Intrinsic Reliability Assessment of 650V Rated AlGaN/GaN Based Power Devices: An Industry Perspective

“…Due to the high electric field and self heating generated in the drain area, degradation of the ohmic contacts can affect device lifetime (16). Au based contacts have proven to be a significant reliability issue at elevated temperatures in GaAs and InGaAs based HEMTs (17).…”

Reliability Investigation of GaN HEMTs for MMICs Applications

“…limiting the use of their full capabilities [3], which are significantly greater of the currently available competing solid-state devices such as Silicon LDMOS and GaAs HEMTs [1].…”