Presentation Information
[16a-W2_401-4]Dependence of 2-dimensional electron gas mobility on temperature and carrier concentration: Evidence of carrier-carrier scattering
〇Markus Pristovsek1, Yoann Robin1, Itsuki Furuhashi1 (1.IMASS, Nagoya Univ.)
Keywords:
mobility,2DEG
III-Nitride-based high electron mobility transistors (HEMTs) have very high sheet carrier densities due to the strong polarization contrast between AlN and GaN. Recently, devices using direct AlN/GaN interfaces have been realized with sheet carrier densities exceeding 8x1013 cm-2 in 10 nm thin channels. However, the temperature-dependent mobility of such high sheet carrier density 2-dimensional electron gases (2DEG) shows a very different behavior than expected. Typically, the temperature-dependent mobility of a 2DEG above 200 K is limited by the optical phonon scattering (µPO) which is characterized by an exp(1/T) dependence. We observed that an additional temperature contribution proportional to 1/T² must be included in the mobility to reproduce our experimental data.
When reviewing the published data of AlGaN/GaN based 2DEGs, we noticed that such a 1/T² contribution is indeed present in most temperature-dependent mobility datasets, more pronounced at higher the sheet carrier densities. Thus, there is a mobility contribution µ~1/(Ns T²) in most 2DEGs. The usual µPO can neither account for the observed temperature dependence, nor for the strong reduction of channel mobility starting around 1.5x1013 cm-2. Hence, we attribute this hitherto unaccounted scattering mechanism to carrier-carrier scattering (probably between different subbands in the 2DEG or including three carrier processes), which ultimately limits the room temperature mobility at very high sheet carrier densities.
When reviewing the published data of AlGaN/GaN based 2DEGs, we noticed that such a 1/T² contribution is indeed present in most temperature-dependent mobility datasets, more pronounced at higher the sheet carrier densities. Thus, there is a mobility contribution µ~1/(Ns T²) in most 2DEGs. The usual µPO can neither account for the observed temperature dependence, nor for the strong reduction of channel mobility starting around 1.5x1013 cm-2. Hence, we attribute this hitherto unaccounted scattering mechanism to carrier-carrier scattering (probably between different subbands in the 2DEG or including three carrier processes), which ultimately limits the room temperature mobility at very high sheet carrier densities.