Question

5.15P) Review a)Figure shows position of the three conduction band minima of Al, Gadi- x)As structure as x changes. I is direct band and X indirect band. (Valance band maximum is 0 eV). For the value of x=0.6 which band do you prefer for to make a photodiode. Why? What should be the wavelength range for this photodiode? b)Plot the plane surfaces given Miller indices of (1 10) and (5 2 3) calculate the surface vector of the surface.(the lattice constant is a) 1.41 1.0 Gaas ALAS

Answer 1

Solution! make a two reasons - gs Photodiode: A semiconductor diode whích, when exposed to light, generates potential difference or changes ita electrical resistance, (current). The wavelength range for this photodiode isa- Value of 1-0.6, indirect band (x) is preferable to photodiode. This Alaga (1-2) forms indirect bandgap for de sous. So, it's preferable for for direct band there is a significant loss due to surface recom bination An indirect bandgap engages photons to conserve momentum, So, the indirect band.. -gap formula: Atg indirect - Atgy x and Atg2-0.476 +0.125% = 1.424 7 A Egz = $424+0.476+(0.125 40 40.6)+(0-14380.62)ev -2.026ev2.03ey. let's calculate wavelength x: - Beg indirect = 663x10-34x3x108 203 x1.6 x 10-19 0.143x2 ha 203 ev. Since m. x = 6.1076x10 m=610.76hm. CS Scanned with CamScanner

So, the wavelength of photodiode=1610.76nM b) Miller Indiçes: - Miller indices form a notation System in crystallography for planes in crystal taltices. In particular, a family of battice planes is determined by three intogers hik and l; the Miller indices. They are written, and denote the family of planes orthogonal to, where are the basis of the reciprocal. lattice vectors: hk l) = (10) So, intercepts at.az - a y=a, z=0 Now, this plane is parallel to Z, normal to the surface of (hk e becomes hâtkût 2² = ît] or lâ+8) is the normal to that surface: CS Scanned with CamScanner

Z y L ty a (110) surface and direction = 9+î ✓ Miller indice (523) a/3 Intercept; a-ay-a i za Direction of this surface is a/2 5 â + 2ĝ+ 37. Miller surface (523) als th CS Scanned with CamScanner

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