No abstract

Interfaces in semiconductor heterostructures is of continuously greater significance in the trend of scaling materials down to the atomic limit. Since atoms tend to behave more irregularly around interfaces than in internal materials, accurate energy band alignment becomes a major challenge, which determines the ultimate performance of devices. Therefore, a comprehensive understanding of the interplay between heterointerface, energy band, and macro‐performance is desiderated. Here, such interplay is explored by investigating asymmetric heterointerfaces with identical fabrication parameters in multiple‐quantum‐well lasers. The unexpected asymmetry derives from the atomic discrepancy around heterointerfaces, which ultimately improves the optical property through altered valence band offsets. Strain and charge distribution around heterointerfaces are characterized via geometric phase analysis and in situ bias electron holography, respectively. Combining experiments with theories, arsenic‐enrichment at one of the interfaces is considered the origin of asymmetry. To reveal actual band alignment, valence band model is modified focusing on the transition around heterojunctions. The enhanced photoluminescence intensity reflects the alleviation of hole confinement insufficiency and the enlargement of valence band offset. The results help to advance the understanding of the general problem of interface in nanostructures and provide guidance applicable to various scenarios for micro–macro correlation.

Effectively restraining random fluctuation of layer thickness (RFT) during the thin-film epitaxy plays an essential part in improving the quality of low-dimensional materials for device application. While it is already challenging to obtain an ideal growth condition for thickness control, the tangle of RFT with interfacial problems makes it even more difficult to guarantee the properties of heterostructures and the performance of devices. In our research, the RFT of potential barriers and wells within a semiconductor multilayer is demonstrated to correlate with the interfacial grading effect (IFG) and to affect the band offset strongly. Then, the synergetic effect of RFT and IFG that serves as the first domino is shown to impact the subband structure and the electron transport successively. On the basis of an investigation of a quantum cascade structure, statistical results indicate a normal distribution of RFT with a standard deviation of about 1 Å and an extreme value of 3 Å (about one monolayer) for all the layers within 38 cascade periods. The "seemingly negligible" RFT could actually reduce the conduction band offset for tens to hundreds of meV and alter the subband gaps at a rate of 40 meV/monolayer at most. Furthermore, the dependence of different subband gaps on the barrier/well thickness differs from one another. In addition, the distribution of wave function could also be regulated dramatically by RFT to change the type of electron transition and thus the carrier lifetime. Further impacts of RFT and the RFT-modulated subband alignment on electron transport result in two different mechanisms (injection-dominant and extractiondominant) of electron population inversion (PI), which is manifested by comparatively discussing the results of in situ electron holography and macro performances.