Charge Profiling of the p-AlGaN Electron Blocking Layer in AlGaInN Light Emitting Diode Structures
- PDF / 79,830 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 11 Downloads / 175 Views
0892-FF19-03.1
Charge Profiling of the p-AlGaN Electron Blocking Layer in AlGaInN Light Emitting Diode Structures Y. Xia1,2, Y. Li1,2, W. Zhao1,2, M. Zhu1,2, T. Detchprohm1,2, E.F. Schubert1,3, and C. Wetzel1,2 1 Future Chips Constellation, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A. 2 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A. 3 Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A.
ABSTRACT Characterization of operational AlGaInN heterostructure light emitting diodes (LEDs) is critical to their performance optimization and time-to-failure analysis. Typically, device performance data needs to be corroborated with structural information such as layer thicknesses, charge profiles, and the absolute location of the pn-junction. Here, non-destructive testing by capacitance-voltage profiling is being applied to AlGaInN LED structures. Within a large set of samples with different active layer geometry, we observe distinct layers of high mobile charge accumulation. We correlate those with layer thicknesses derived from an x-ray diffraction analysis of the corresponding epiwafers. In this way, we identify the charge maxima as the upper and lower interfaces of the p-type AlGaN electron blocking layer to the neighboring GaN layers. By means of this successful analysis, we now have the opportunity to monitor epi process performance and stability as well as device degradation progress quasi-continuously over the device lifetime in a non-destructive mode.
INTRODUCTION Group – III nitride light emitting diodes (LEDs) are the prime candidate for energy efficient all solid state lighting in the blue and green spectral region. Active regions comprising GaN/GaInN multi quantum well (MQW) heterostructures act as light emitters, while adjacent GaN and AlGaN layers form a pn-junction to inject electrons and holes, respectively. A critical problem is the controllably and stable injection of either carriers under various operating conditions. A p-type AlGaN electron blocking layer serves to reduce an electron overshoot into the p-layers. Placement, doping, and dimensions thereof are deemed critical to the stabilization of the injection conditions at variable drive current densities. Capacitance-voltage (C-V) measurements have widely been used to investigate such properties in, among others, the AlGaAs/GaAs, InGaAlP/GaAs and ZnO/GaN heterostructure systems.[1-3] Very little, however, is known for LEDs in the AlGaInN system. Recently we succeeded in resolving in individual quantum wells GaN/GaInN active layers.[4] Electric pulse and probe spectroscopy in time domain of forward biased LEDs has been applied by the Sandia group.[5] Here we report an analysis of the p-type AlGaN electron blocking layer in LED-type structures similar to those of blue and green GaN/GaInN MQW LEDs. We correlate C-V data with results of x-ray diffraction (XRD) and find good agreement.
0892-FF19-03.2
EXPERIMENTAL LED-
Data Loading...
