The Photomagnetoelectric Effect in Mercury Iodide
In order to investigate the transport properties of mercury iodide, measurements of photomagnetoelectric (PME) effect and photoconductivity (PC) have been carried out. The experimental results show the presence of trapping phenomena and a strong dependence of carrier lifetimes on the light injection level. The obtained values of the lifetimes are in the range 10-7-10-6 s.
Investigation of the Recombination and Trapping Processes of Photoinjected Carriers in Semi‐Insulating Cr‐Doped GaAs Using PME and PC Methods
Investigation of the recombination and trapping processes of photoinjected carriers in semi‐insulating Cr‐doped GaAs (ρ ∼ 108 Ω cm) has been made at 80 and 300°K, using the photomagnetoelectric (PME) and photoconductive (PC) effects under large‐injection conditions. A generalized theory for the PME and PC effects is developed, taking into account the variation of carrier lifetimes with injected‐carrier density (i.e., τn = κΔnβ) and of the trapping of holes in the Cr levels (i.e., Δp = ΓΔn, Γ<1), by using a simple recombination and trapping model. The result yields a power‐law relationship between the PME short‐circuit current and the photoconductance, in a form that IPME varies as ΔG2/(2+β), valid for different injection ranges. Two well‐defined ranges of injection were observed from the present results: In region I (high injection), IPME is directly proportional to ΔG (i.e., β = 0), and in region II (intermediate injection), IPME varies with ΔG1.2 (i.e., β = −⅓). Numerical values of τn, τp, and IPME as f...
Indirect Energy Gap in GaSe and GaS
Optical absorption measurements on thick monocrystalline samples of GaSe1−xSx show that in these mixed crystals the lowest energy gap is indirect in the complete range 0 ≦ x ≦ 1. These results are contrary to earlier reports which indicate that GaSe is a direct gap semiconductor. In the case of GaS the absorption spectra allow a tentative identification of the phonons involved in the indirect transition. 
 
 
 
Optische Absorptionsmessungen an dicken, einkristallinen Proben von GaSe1−xSx zeigen, das der kleinste Bandabstand in diesen Mischkristallen im ganzen Bereich 0 ≦ x ≦ 1 einem indirekten Ubergang entspricht. Dieses Resultat steht im Widerspruch zu fruheren Ergebnissen, denen zufolge es sich bei GaSe um einen Halbleiter mit direktem Ubergang handelt. Die Absorptionsspektren des GaS lassen eine vorlaufige Identifizierung der am indirekten Ubergang beteiligten Phononen zu.