Low-temperature carrier transport across InGaN multiple quantum wells: Evidence of ballistic hole transport

Carrier transport across polar n -type InGaN/GaN multiple quantum wells (MQWs) has been studied by time-resolved photoluminescence (PL) using an optical marker technique. Efficiency of the hole transfer into the marker well experienced a nonmonotonous temperature dependence. First, as the temperature was lowered below room temperature, the number of transferred holes decreased because of the decreased efficiency of the thermionic emission. However, when the temperature was lowered below ∼80 K, the number of transferred holes experienced a significant rise. In addition, the low-temperature hole transport across the MQW structure was very fast, <3 ps. These features indicate that the low-temperature hole transport across the MQWs is ballistic or quasiballistic. Comparison of PL data for structures with different MQW parameters suggests that at low temperatures the hole mean-free path is about 10 nm. Probably, hole transport via light hole and split-off valence bands contributes to this high value.