Electro Optical Characterisation of Short Wavelength Semiconductor ...
Data Analysis levels of the quantised states. To do this simulation, the 1D Schrödinger-Poisson solver software written by Prof. G. Snider from the university of Notre Dame, USA, has been used . The results of the Current [A] 0,25 0,2 0,15 0,1 0,05 CW I/V g0942/1um Si:AlGaN g0937/1.5um Si:AlGaN g0938/2um Si:AlGaN 0 0 5 10 Voltage [V] 15 20 Figure 4.22: Threshold voltage shifting simulation don’t seem that satisfying. The cladding layer thickness of the structures seem to be the only difference with no influence on the energy barriers. Fig. 4.23 shows the conducting band energy of all three series versus the thicknesses with an applied voltage of +10V to overcome the energy barriers of all three due to Fig. 4.22. The calculated barriers are energetically absolutely coinciding. Even the energies of the waveguide, as a merging peak between the cladding layer and the quantum wells, seem to be similar. From that all could be concluded that either the crystal structures of the named series are not completely similar, so that the input information to the software doesn’t match to the reality, or the method being used in this software (see Appendix C) doesn’t fit this problem. 4.2.2 GaN results in brief All devices coming from series g0937, g0938 and g0942 were LEDs. The unhappy consequence of this fact is that the structures couldn’t have been tested of reduced bulk luminescence. In case of the g0938 series (2µm Si:AlGaN cladding layer) the devices had all very rough 50
GaN Devices Figure 4.23: Conducting band energy barriers vs. thickness of the layers; calculated for all three series. to cracked surfaces. This is due to the thick cladding layer. g0975 series were generally speaking successful. Except for some problems mostly by the thinner ridges and due to the technology, they were capable. Mirroring turned up to be of great importance to increases the functionality of the laser devices. 51
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