Nitrides Seminar - Dr. Erin Young, Postdoctoral Researcher

1/27/2017 12PM ESB 2001

Title:  Calcium impurity as a source of non-radiative recombination in (In,Ga)N grown by MBE



Abstract:  Despite exhibiting excellent electrical properties including world record electron mobilities, high structural quality, and low levels of standard atmospheric impurities such as H,C and O, (In,Al,Ga)N alloys grown by molecular beam epitaxy have traditionally shown very poor radiative efficiency in optoelectronic devices.  Recently we have discovered that MBE material grown both at UCSB and in other laboratories worldwide systematically contains high levels (up to ~1E18 /cm3) of an impurity element, calcium, and have experimental evidence that this defect may act as a Shockley Read Hall recombination center in MBE alloys.  We have investigated the incorporation of Ca as a function of MBE growth conditions and demonstrated a way to grow MQW active regions with reduced Ca concentration via low temperature buffer layers.  Preliminary LEDs grown with Ca reduction in the QWs show higher output power than those with high Ca concentration in in the QWs.  In this talk I will give an overview of these studies and the potential implications for light emitting devices grown by MBE.