Over the last 25 years, radiowave detection of neutrino-generated signals, using cold polar ice as the neutrino target, has emerged as perhaps the most promising technique for detection of extragalactic ultra-high energy neutrinos (corresponding to neutrino energies in excess of 0.01 Joules, or 1017 electron volts). During the summer of 2021 and in tandem with the initial deployment of the Radio Neutrino Observatory in Greenland (RNO-G), we conducted radioglaciological measurements at Summit Station, Greenland to refine our understanding of the ice target. We report the result of one such measurement, the radio-frequency electric field attenuation length $L_\alpha$. We find an approximately linear dependence of $L_\alpha$ on frequency with the best fit of the average field attenuation for the upper 1500 m of ice: $\langle L_\alpha \rangle = ( ( 1154 \pm 121) - ( 0.81 \pm 0.14) \, ( \nu /{\rm MHz}) ) \,{\rm m}$ for frequencies ν ∈ [145 − 350] MHz.

We show that the strong bowing of the bandgap of GaInN, which is primarily due to bowing of the valence band edge, translates into a strongly composition dependent ratio of the conduction band offset to the valence band offset with respect to GaN. For common In mole fractions of 0-20 % this leads to a reversal of the band offset ratio and to very weak electron con nement. This theoretical picture is veri ed by comparing results of time-resolved spectroscopy on asymmetric AlGaN/GaInN/GaN and AlGaN/GaN/AlGaN quantum wells. Since electron con nement is much stronger for GaN/AlGaN wells than for GaInN/GaN wells, the effect of asymmetry is very weak for the former and fairly strong for the latter.