Abstract
Magnetic transport spectroscopy is investigated in quantum point contacts (QPCs) fabricated in Al0.25Ga0.75N/GaN heterostructures. The magnetic field perpendicular to the two-dimensional electron gas (2DEG) is shown to depopulate the quasi-one-dimensional energy levels in the first two-dimensional (2D) subband faster than those in the second one. In GaN based heterostructures, the energy levels in the second 2D subband is generally concealed in the fast course of depletion and hence rarely detected. The perpendicular magnetic field facilitates the observation of the second 2D subband, and provides a method to study the properties of these energy levels. A careful analysis on the rate of the magnetic depletion with respect to the level index and confinement is carried out, from which the profile of the lateral confinement in GaN based QPCs is found to be triangular. The stability diagram at T shows the energy separation between the first and second 2D subband to be in the range of 32 to 42 meV.
Highlights
Magnetic transport spectroscopy is investigated in quantum point contacts (QPCs) fabricated in Al0.25Ga0.75N/GaN heterostructures
Due to its relatively high mobility2,3, long spin lifetime4, and strong spin-orbit coupling (SOC)5,6 induced by the strong build-in electric field due to the large spontaneous and piezoelectric polarization7,8, the studies of spin related physics are attractive
Recent experiments proved an exciting possibility of using QPCs for spin injection and detection for spin field effect transistors9,10, yet little has been studied about the transport properties in GaN based QPCs
Summary
The Al0.25Ga0.75N/GaN heterostructures were grown on c-plane sapphire substrates by means of metal organic chemical vapor deposition (MOCVD). A large Rashba spin-orbit coupling in the 2DEG, while preserving a relatively high electron mobility Such structure forms a deep and narrow triangular quantum well at the hetero-interface, inducing a 2DEG with high carrier concentration, in which the electrons may even occupy the second subband. Such structure forms a deep and narrow triangular quantum well at the hetero-interface, inducing a 2DEG with high carrier concentration, in which the electrons may even occupy the second subband11,12 It takes a gate voltage of more than −8 V to deplete the 2DEG beneath the gate area, the influence of which appear in the measurements and in the fabrication process. A brief summary of the measured QPCs is given in the supplemental material
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
