Sidewall lateral epitaxial overgrowth (SLEO) of non-polar a-plane and m-plane GaN that results in several device improvements such as longer lifetimes, less leakage current, more efficient doping and higher output efficiency.
It is relatively easy to grow c-plane GaN due to its large growth window (pressure, temperature and precursor flows) and its stability. However, as a result of c-plane growth, each material layer suffers from separation of electrons and holes to opposite faces of the layers. Furthermore, strain at the interfaces between adjacent layers gives rise to piezoelectric polarization, causing further charge separation. Such polarization effects decrease the likelihood of electrons and holes recombining, causing the device to perform poorly. Another reason why GaN materials perform poorly is the presence of defects due to lack of a lattice matched substrate. There is an ever-increasing effort to reduce the dislocation density in GaN films in order to improve device performance.
Researchers at the University of California, Santa Barbara have successfully developed sidewall lateral epitaxial overgrowth (SLEO) of non-polar a-plane and m-plane GaN. By using single step lateral epitaxial overgrowth, dislocation densities can be reduced and stacking faults are localized only on the nitrogen faces. Dislocation densities can be reduced down to even lower values by eliminating defects not only in the overgrown regions but also in the window regions. Also, by favoring gallium (Ga) face growth and limiting nitrogen (N) face growth stacking fault densities can be made orders of magnitude lower. The present invention also takes advantage of the orientation of non-polar III-Nitrides to eliminate polarization fields. As a result, with the material produced by utilizing this invention, device improvements such as longer lifetimes, less leakage current, more efficient doping and higher output efficiency are possible. In addition, a thick non-polar and semi-polar nitride free-standing substrate, which is needed to solve the lattice mismatch issue, can be produced over this excellent material.
This technology is available for a non-exclusive license. See below for a selection of the patents and patent applications related to this invention. Please inquire for full patent portfolio status.
|United States Of America||Issued Patent||7,955,983||06/07/2011||2005-565|
|United States Of America||Issued Patent||7,361,576||04/22/2008||2005-565|
indssl, indled, GaN, III-Nitrides, cenIEE