Contents

1. Introduction____________________________________________________________ 1

2. Electrons in III-V semiconductor heterostructures_____________________________ 4

3. Time-resolved measurement method _______________________________________ 16

4. Electron-electron scattering and the D’Yakonov-Perel mechanism in a high mobility

electron gas _______________________________________________________________ 22

4.1 Introduction _______________________________________________________ 22

4.2 Background _______________________________________________________ 23

4.3 Theory____________________________________________________________ 25

4.3.1 Conduction band spin-splitting and the D’yakonov-Perel mechanism _______ 25

4.3.2 Evolution of spin polarisation excited in the valance band ________________ 28

4.3.3 Energy distribution of the electron spin polarisation _____________________ 29

4.4 Sample description__________________________________________________ 32

4.4.1 Sample mobility _________________________________________________ 34

4.4.2 Optical characterisation ___________________________________________ 36

4.5 Experimental procedure _____________________________________________ 38

4.6 Results____________________________________________________________ 38

4.7 Analysis___________________________________________________________ 44

4.7.1 Monte-Carlo simulation ___________________________________________ 45

4.7.2 Electron-electron scattering ________________________________________ 47

4.7.3 Spectral sampling of the conduction band spin-splitting and anisotropy ______ 48

4.8 Summary and conclusions____________________________________________ 55

4.9 References_________________________________________________________ 57

5. Spin relaxation in undoped InGaAs/GaAs quantum wells ______________________ 60

5.1 Introduction _______________________________________________________ 60

5.2 Background and theory______________________________________________ 61

5.2.1 Exciton spin dynamics ____________________________________________ 62

5.2.2 Effects of temperature_____________________________________________ 67

5.3 Sample description__________________________________________________ 71

5.4 Experimental procedure _____________________________________________ 71

5.5 Results____________________________________________________________ 74

5.6 Analysis___________________________________________________________ 94

5.7 Interpretation______________________________________________________ 99

5.7.1 Phases in the evolution of the excited population_______________________ 100

5.7.2 Exciton thermalisation ___________________________________________ 101

5.7.3 Thermalised excitons ____________________________________________ 103

5.7.4 Comparison with InGaAs/InP, the Native Interface Asymmetry___________ 107

5.7.5 Dynamics of the unbound e-h plasma and carrier emission _______________ 108

5.8 Summary and conclusions___________________________________________ 112

5.9 References________________________________________________________ 114

6. Exciton spin precession in a magnetic field_________________________________ 117

6.1 Introduction ______________________________________________________ 117

6.2 Background and theory_____________________________________________ 118

6.3 Sample description_________________________________________________ 124

6.4 Experiment _______________________________________________________ 125

6.5 Results___________________________________________________________ 127

6.6 Summary and Conclusions __________________________________________ 140

6.7 References________________________________________________________ 141

7. Conclusions__________________________________________________________ 143

7.1 References________________________________________________________ 146

8. List of Publications ____________________________________________________ 14