Ponentes: M.Sc. Julia Sławińska y Prof. Czesław Skierbiszewski.
Organismo: Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw. Poland.
Fecha: 16 de noviembre 2021
Hora: 12.00 horas
Lugar: Salón de Grados, edificio A de la ETSIT.
Poor conductivity of the p–type region and difficulties with processing of low resistance ohmic p–type contacts are the most challenging issues to address in nitride based devices. Recently, there has been increasing attention given to the interband tunnel junctions (TJs) for efficient carrier conversion between n–type and p–type material region in nitride devices. Application of TJs eliminates the need for p–type contact deposition and create more freedom in device design. It was clearly demonstrated that TJs resistance for wide bandgap semiconductors can be effectively reduced by making use of the piezoelectric fields in the region of the junction. However, for metal–organic vapour phase epitaxy (MOVPE) it is difficult to activate the p–type conductivity in the (In)GaN:Mg layers which are buried below n–type layers due to the fact that diffusion of hydrogen is completely blocked through n–type region. On the other hand, for plasma assisted molecular beam epitaxy (PAMBE) p–type doping is achieved without post growth activation process. Therefore, PAMBE seems to be better suited than MOVPE for practical realization of the vertical devices with buried p–type regions – especially for devices containing interband TJs. In this work we will show current status of III–N TJs grown by PAMBE. Application of TJs enabled us to demonstrate novel types of III–N devices, like: (1) vertically integrated light emitting diodes (LEDs) or laser diodes (LDs), (2) distributed feedback LDs. We will discuss in detail the inverted LED structures, operating at cryogenic temperatures. These LEDs contain the TJs below active region, which allow to reverse electric polarization of the diode. The application of TJs opens a possibility for novel architecture of micro–LEDs. We show an alternative method of nitride micro–LEDs fabrication, where emission surface was defined by size of the TJ embedded inside diode. Micro–LEDs and arrays of micro–LEDs will be presented.