Temperature-Dependcnt Growth of InP By Plasma-Enhanced GSMBE

Abstract

<p>This thesis reports on study of the effects of various plasmas on the growth of InP films by GSMBE. The samples were grown at temperatures ranging from 232 to 500°C. The plasmas were generated by electron cyclotron resonance, giving a broad distribution of ion energies in the 10-50 cV range. H. D, He and Ar plasmas were studied. Films were also grown at the same temperatures without plasma, as references.</p> <p>The samples were characterized by: Nomarski phase contrast microscopy, Xray double crystal diffraction, Hall effect measurements, photoluminescence (PL), variable-energy positron annihilation, thermal desorption, nuclear reaction analysis and capacitance/voltage profiling. The Xray, Hall and PL measurements were repeated after the samples were annealed at 730°C for 10 seconds. In no case was the material produced of comparable quality to that grown under standard conditions (465°C, no plasma).</p> <p>The films grown without plasma were n-type, reaching a carrier concentration of approximately 2x10¹⁸/cm³ at 300°C. This is in agreement with published results, which showed that the donor defect responsible is a P atom on an In site. This defect occurred in sufficiently high concentrations to mask the effects of the plasmas below 400°C.</p> <p>H plasma increased the carrier concentration by approximately 7x10¹⁶/cm³. Some H atoms appear to bond to P atoms in the crystal, resulting in an excess In electron. The carrier concentration was not affected by annealing. Additional H atoms may be present as interstitials, causing a reduction in mobility and a broad PL peak near 1.05 eV. These effects were removed by annealing.</p> <p>D plasma produced similar effects to H plasma, but the carrier concentration and mobility were lower. P interstitials, which act as deep acceptors, may be produced by recoiling surface P atoms into the bulk. Beryllium dopant, at a concentration of 2x10¹⁸/cm³), was passivated by this plasma. Silicon dopant was not strongly affected.</p> <p>He plasma produced P interstitials and P vacancies, by recoil displacement from the surface and in the bulk. More P interstitials were produced, compensating up to 10¹⁷/cm³ carriers. The interstitials were more mobile, diffusing out during the 500°C growth and during annealing.</p> <p>The effects of the Ar plasma were small enough to be masked by the weak H plasma that results from H backstreaming.</p> <p>Films grown at 400°C or less without plasma had textured surfaces. The plasmas usuaIly smoothed the surfaces at these temperatures, resulting in defect densities lower even than occured at 465°C without plasma. Above 400°C. none of the plasmas significantly affected the surface defect densities.</p>