Ion Etching Effects Occurring in Secondary Ion Mass Spectrometry Depth profiling of InGaAs/InP and InGaAs/AlAs/InP MBE Grown Heterostructures

Abstract

Depth profiling analysis of In x Ga1x As heterolayers grown by MBE on Fe doped InP(100) substrates was performed in the SAJW-02 secondary ion mass spectrometry analyser equipped with 4.5 keV O+2 ion source and a specially designed sample manipulator enabling depth profiling in the standard as well as in so-called Zalar rotation operation modes. The fairly high energy of the primary ion beam required for sputtering in secondary ion mass spectrometry measurements causes changes in surface topography, usually of different origin. Depth resolution parameters and roughness formation monitored by scanning electron microscopy were analysed for a set of samples with composition x changing in the range 0.33 to 0.60. The results were compared with the same data for a layer of z = 0.53 (best lattice-matched to InP) grown on the top of a three monolayer thick AlAs film deposited previously on the InP substrate. Improvement in the depth profile resolution was revealed for the structure with an AlAs layer indicating sharper interface transition. Moreover, sample rotation applied for this structure improves further the depth profaling resolution. Thus, we showed for the first time that a very thin AlAs layer grown by MBE between the InP substrate and the m053 Ga047 As improves considerably the heterointerface properties and that Zalar rotation applied for depth profiling of the investigated material system diminishes further the negative effects of ion etching on depth resolution in secondary ion mass spectrometry analysis.