Electrical Characterization of ALD Al2O3/AlN/GaN HEMTs and Integration with Microano Magnets for Novel Device Application

The III-Nitrides are direct band gap semiconductors that span a large range of band gaps from ~0.6 eV (InN) to 6.2 eV (AlN). In recent years High Electron Mobility Transistors (HEMTs) based on III-Nitride semiconductors have proved capable of high power, high voltage and high frequency operation. Integration of ALD oxides with GaN will enable lower gate leakage currents, high breakdown voltages, and surface passivation of HEMTs. In this work we present a comprehensive characterization of AlN/GaN MOS-HEMT (grown by PAMBE) gate stacks with ALD Al2O3 of various thicknesses. Through capacitance-voltage and Hall-effect measurements, we find the presence and propose an origin of benign donor-type interface charge Qit~ 6x1013 cm-2 at the AlN/Al2O3 junction, and relate its presence to the polarization charges in AlN. The role of ALD oxygen layers as possible modulation dopants can offer opportunities for various innovative designs in III-Nitride electronic devices. Most importantly by controlling the effective Qit (for example by compensation doping, or by varying the polarization through the composition), pinch-off voltage Vp can be made to increase, remain independent, or decrease with dielectric thickness tox.

There is a strong recent interest in studying the effect of magnetic interaction of various ferromagnetic structures leading the pathway for nanomagnet logic operation (NML). However, there is a very little effort so far to identify the potential effect of high current density of III-Nitride heterostructure on microanomagnetic structures High-current drive nitride devices can potentially eliminate the need for auxiliary arrangements of switching and may enable the integration of logic and memory in the same device. The successful integration of microano magnets (supermalloy made) with III-Nitride heterostructure and the ability of imaging the single/multi-domain featured nano/micromagnets on III-Nitrides presented in this work opens the possibility of active device driven switching of nanomagnets in MQCA logic operation. Although simulation result has shown that the field requirement in nanomagnet switching is higher compared to the H field obtained (~1mT) using the drain current (1.4Amps/mm) of a normal HEMT, it is possible to use other nitride structures (n-GaN) to deliver current density more than 10amps/mm as shown in this work. Such a high current density produces a magnetic field in excess of 8mT. This field can be used affectively to move the domains of the micromagnetic structures, and possibly nanomagnets switching too.