Abstract
In this article, we separately investigate the role of electric field and device self-heating (SHE) in enhancing the charge emission process from Fe-related buffer traps (0.52 eV from ${E}_{c}$ ) in AlGaN/GaN high electron mobility transistors (HEMTs). The experimental analysis was performed by means of drain current transient (DCT) measurements for either: 1) different dissipated power ( ${P}_{D,\mathrm {steady}}$ ) at constant drain-to-source bias ( ${V}_{\mathrm {DS,steady}}$ ) or 2) constant ${P}_{D,\mathrm {steady}}$ at different ${V}_{\mathrm {DS,steady}}$ ’s. We found that: 1) an increase in ${P}_{D,\mathrm {steady}}$ yields an acceleration in the thermally activated emission process, consistently with the temperature rise induced by SHE and 2) on the other hand, the field-effect turned out to be negligible within the investigated voltage range, indicating the absence of the Poole–Frenkel effect (PFE). A qualitative analysis based on the electric field values obtained by numerical simulations is then presented to support the interpretation and conclusions.
Highlights
AlGaN/GaN high electron mobility transistors (HEMTs) are expected to play an important role in generation RF communications systems, due to their high power and high frequency capability [1] that make them interesting for the upcoming 5G revolution [2]
The trap-filling pulse parameters were chosen to deliberately induce a relatively small current variation (~4 mA/mm) to avoid excessive perturbation of the steady-state operating point. This choice was mainly motivated by the following considerations: i) a large current variation would change significantly the dissipated power during the monitored transient [17], whereas a small perturbation does not affect the power set in steady-state condition, yielding negligible temperature variations; ii) a small current variation is representative of a low amount of trapped charge variation [30,31,32], whose dynamics is expected to not significantly alter the electric field profile during the drain current transient (DCT)
We found that self-heating produces a consistent acceleration in the thermally activated emission process, as a result of the temperature rise in the device active region
Summary
AlGaN/GaN high electron mobility transistors (HEMTs) are expected to play an important role in generation RF communications systems, due to their high power and high frequency capability [1] that make them interesting for the upcoming 5G revolution [2]. Exploiting the whole potential of GaN-based power HEMTs still represents an open challenge due to dispersion phenomena limiting their performance and reliability [3] In this regard, deep-levels related to intentional or undesired impurities incorporated during material growth or device fabrication induce trapping effects that severely affect the large signal operation. To assess the dependence of the Fe-traps emission rate on SHE and electric field, we perform Drain Current Transient (DCT) measurements [23,24] starting from properly chosen bias conditions to evaluate these two concurrent effects separately.
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