Thermionic escape of net photogenerated carriers and current densities from illuminated lightly doped single quantum wells

✍ Scribed by Argyrios C Varonides

• Book ID: 104428111
• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 172 KB
• Volume: 14
• Category: Article
• ISSN: 1386-9477
• DOI: 10.1016/s1386-9477(02)00367-3

✦ Synopsis

Photogenerated carriers captured in the intrinsic region of p=i=n GaAs-AlGaAs quantum well systems and contributing to current densities after thermionic escape, is the purpose of this communication. Illuminated intrinsic regions of solar cells with multiple quantum wells are expected to contribute an increase to overall collected currents when compared to bulk p=i=n solar cells. Carriers of the order of 10 12 cm -2 are found to be generated in single quantum wells of the i-region, and under 10 17 =cm 2 =s 1 steady illumination ux levels (under Auger and radiative recombination mechanisms taken into account). Next, the contribution from each quantum well is evaluated in the form of thermionic current density values, and in terms of temperature and individual quasi-Fermi level position relative to the fundamental miniband in each well. Based on analytic results (for 30% Al fraction, and for 3-10 nm lightly doped GaAs layers), computations show that (a) current density may vary from 1 to 9 mA=cm 2 =10 nm quantum well, as a function of background doping level in the neighborhood of 10 11 -10 12 cm -3 , and at three representative temperatures -10

• C; 27 • C, 40

• C (b) current density may vary from 0.1 to 0:9 mA=cm 2 for a range of widths from 3 to 10 nm, at the same temperatures, and for similar background doping (c) lightly doped 10 nm GaAs quantum wells may generate current densities varying from 0.1 to 0:8 mA=cm 2 under photo-carrier levels in the order of 10 12 cm -2 , and room temperature.