Significant energy relaxation of quantum dot emitted hot electrons

Mesoscopic quantum dots (QDs) are ubiquitous in devices as reliable sources of hot electrons. However, we have observed an unexpectedly significant energy relaxation QD-emitted electrons up to $\ensuremath{\approx}55%$ its excitation $\ensuremath{\le}1.5\phantom{\rule{4pt}{0ex}}\mathrm{meV}$ from the Fermi level. The energetics were obtained through transverse magnetic focusing over a few microns using both QD and point contact (QPC) emitters. Unlike QPC counterparts, emissions deviated substantially gas predictions---the peak appeared at lower fields, excessive broadening was observed. phenomenon modeled by capacitive interaction transferring electron QD. Model simulations reproduced key experimental features, implying presence strong yet overlooked mechanism that is intrinsic emissions. Our observation calls for prudent use QDs single sources.