Electro Optical Characterisation of Short Wavelength Semiconductor ...

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Data Analysis Following the trend of decreasing threshold current density with increased ridge depth this value matches good in the measurements done in this thesis (see Table 4.5 and Fig. 4.10). It is worth mentioning that the crystals at the time of publishing this work are over 4 years old and have become obsolete. Fig. 4.9 shows the I/V behaviour and the spectrum of an exemplary chosen device. The Current [mA] 400 300 200 100 measured curve fitted curve tangent s1172/600nm/10um i/v 0 0 5 10 Voltage [V] 15 20 Cts/s 2e+05 1,5e+05 1e+05 50000 s1172/600nm/10um spectrum 0 510 515 520 525 Wavelength [nm] 530 535 540 Figure 4.9: I/V behaviour as well as spectrum of a device belonging to the 600nm series. threshold voltage doesn’t show any immense differences to the cases already had. The spectrum demonstrates a stronger multimode lasing than in case of 6µm ridge width. Let’s put it this way, there is no good reason because of which a non-multimode lasing occurs when a length of approximately a millimetre of the active region a trouble-free cohabitation of standing waves with different wavelengths guarantees. 4.1.2 ZnSe results in brief Table 4.5 shows the average values of all the lasing devices measured in each category i . As already mentioned a decreasing trend is observable from left to right of each row. This is due to the aimed current apply to the active zone. It is possible to depict this trend dependent on the ridge depth (see Fig. 4.10). The error bars shown are the differences between the highest and the lowest threshold current density measured, applied on both sides of the average value. The deeper the ridge the smaller the divergence in measured valued. In order to be able to compare these results with the older measurements the average value of the threshold current density mentioned in the thesis of A. Gust [44] have been obtained for the 10µm ridge, planar structure. Fig. 4.10 shows that even this earlier value obeys the trend expected in the structures. The threshold voltage values were all more or less the same and not too satisfying which 38 i Please find the whole values measured, from which these averages are calculated, in Appendix B
planar 600nm 1200nm 1800nm 2µm LED 3895.45 A/cm 2 2505.3 A/cm 2 defect (1360.53 µm) (1098.42 µm) 6µm 2864.46 A/cm 2 1113.30 A/cm 2 844.41 A/cm 2 689.98 A/cm 2 (1115.39 µm) (1083.55 µm) (1192.75 µm) (1083.91 µm) 10µm LED 1213.77 A/cm 2 745.94 A/cm 2 849.1 A/cm 2 1370 A/cm 2 † (1390.10 µm) (1024.79 µm) (1066.35 µm) † this value is obtained from the A. Gust’s thesis [44] ZnSe Devices Table 4.5: Average threshold current density values. The values in the parentheses are the average lengths of the devices. threshold current [A/cm 2 ] 4000 3000 2000 1000 0 threshold current vs. ridge depth 2um 6um 10um obtained 0 600 1200 1800 ridge depth [nm] Figure 4.10: The average value of threshold current density vs. the depth of the ridge structure. 39
Page 1: University of Bremen Technical Univ
Page 4 and 5: Preface ing the characterisation me
Page 6 and 7: CONTENTS 4.2.1 Characterisation of
Page 8 and 9: Basic Concepts Semiconductor lasers
Page 10 and 11: Basic Concepts many problems appear
Page 12 and 13: Basic Concepts 1.2.2 Light in Cryst
Page 14 and 15: Basic Concepts which by using 1.6 c
Page 16 and 17: Basic Concepts Eq. 1.19 delivers di
Page 18 and 19: Basic Concepts light below the mate
Page 20 and 21: Developing Laser Diodes Metalorgani
Page 22 and 23: Developing Laser Diodes 18 4. Lift
Page 25 and 26: Chapter 3 Characterisation Life can
Page 27 and 28: 3.1.3 SEM & FIB Opto-Electrical Cha
Page 29 and 30: voltmeter current source + − 000
Page 31: current source + − 000 111 000 11
Page 34 and 35: Data Analysis As it can be seen the
Page 36 and 37: Data Analysis Output Light Power [W
Page 38 and 39: Data Analysis trometer. This could
Page 40 and 41: Data Analysis Current [mA] 400 300
Page 44 and 45: Data Analysis can be due to the sub
Page 46 and 47: Data Analysis It is worth mentionin
Page 48 and 49: Data Analysis for the whole devices
Page 50 and 51: Data Analysis Figure 4.18: Optical
Page 52 and 53: Data Analysis current density 1.75
Page 54 and 55: Data Analysis levels of the quantis
Page 57 and 58: Chapter 5 Summary and Outlook Great
Page 59: Appendix A Electrical Sources & Mea
Page 62 and 63: ZnSe threshold current density valu
Page 65 and 66: Bibliography [1] N. G. Basov, O. N.
Page 67: BIBLIOGRAPHY [56] G. Snider, 1D Poi

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