Characterization of AlxGa1_xAs layers grown on (100) GaAs by Inetallic-arsenic-based-MOCVD

Abstract

We present the electrical and structural characterization of AlxGa 1 _ xAs layers grown in a metallic­ arsenic-based-MOCVD system. The gallium and aluminium precursors were the metal-organic compounds trimethylgallium (TMGa) and trimethylaluminium (TMAI), respectively. AlxGa 1 _xAs layers that were grown at temperatures less than 750 'C present a high electr ical resistivity. Independent of the used lll /V ratio the samples that were grown at temperatures greater that 750 •c were n-type with an electron concentration of around 1017 cm -3 and a carrier mobility of 2200 cm2 JV-s. Chemical composi­ tion studies by SIMS exhibit the prese nce of silicon, carbon and oxygen as the main residual impurities. Sil icon concentration of around of 1017 em 3 is very close to the free carrier concentration determined by the Hall-van de r Pauw measurements. Composition homogeneity and structura l quality are demon­ strated by Raman measurements. As the growth temperature is increased th e layers compen sation decreases but the Raman spectra show that the crystalline quality of the layers diminishes.