2. (a) Assuming Anderson's rule and Vegard's law calculate the depth of the confining potential in meV, for holes in the valence band of a InAs/InxGa1-xAs multi QW structure where x-0.5. [5]...
2. (a) Assuming Anderson's rule and Vegard's law calculate the depth of the confining potential in meV, for holes in the valence band of a InAs/InxGa1-xAs multi QW structure where x-0.5. [5] State whether electron and hole confinement is within the InAs or InGaAs layers, and hence deduce what type of structure/band alignment this is. Suggest why this structure might be difficult to grow experimentally. (b) A Gao.47lno.53As quantum well laser is designed to emit at 1.55um at room temperature Using an infinite barrier approximation, where the energies of the confined states (En) of a particle of mass m* is given by where m* is the carrier effective mass, show that the width of the quantum well (L) is of the order of 14nm. 4 (c) With the aid of suitably defined equations and/or annotated sketches, explain how the classical Hall effect at low field can be used to deduce the carrier density of a semiconductor two dimensional electron gas (2DEG) sample Describe what happens to the Hall voltage when the field is raised above the quantum limit (wcti > 1), where ae is the cyclotron frequency and τ¡ is the quantum lifetime Note Bandgap Eg Electron affinity () Electron effective mass (Gao.47lno.s3As) m0.041mo Heavy hole effective mass (Gao47lnos3As) mh0.470mo Rest mass of the electron mo 9.1x10-31 kg Eg (InAs) 0.36eV, Eg (GaAs) 1.42eV y (InAs) -4.90eV, x (GaAs) -4.07eV,
2. (a) Assuming Anderson's rule and Vegard's law calculate the depth of the confining potential in meV, for holes in the valence band of a InAs/InxGa1-xAs multi QW structure where x-0.5. [5] State whether electron and hole confinement is within the InAs or InGaAs layers, and hence deduce what type of structure/band alignment this is. Suggest why this structure might be difficult to grow experimentally. (b) A Gao.47lno.53As quantum well laser is designed to emit at 1.55um at room temperature Using an infinite barrier approximation, where the energies of the confined states (En) of a particle of mass m* is given by where m* is the carrier effective mass, show that the width of the quantum well (L) is of the order of 14nm. 4 (c) With the aid of suitably defined equations and/or annotated sketches, explain how the classical Hall effect at low field can be used to deduce the carrier density of a semiconductor two dimensional electron gas (2DEG) sample Describe what happens to the Hall voltage when the field is raised above the quantum limit (wcti > 1), where ae is the cyclotron frequency and τ¡ is the quantum lifetime Note Bandgap Eg Electron affinity () Electron effective mass (Gao.47lno.s3As) m0.041mo Heavy hole effective mass (Gao47lnos3As) mh0.470mo Rest mass of the electron mo 9.1x10-31 kg Eg (InAs) 0.36eV, Eg (GaAs) 1.42eV y (InAs) -4.90eV, x (GaAs) -4.07eV,