Using low frequency noise method to characterize an AlGaAs/GaAs high electron mobility heterostructure S. Mouetsi 1. Département de génie électrique, Faculté des sciences, Université Ibn Khaldoun, Tiaret. Algérie. 2. LMI, Département d’Electronique, Faculté des Sciences de l’Ingénieur, Université Mentouri de Constantine, Algérie. E-mail: souheil.mouetsi@univ-reims.fr A. El Hdiy Laboratoire de Microscopies et d’Etude de Nanostructures (EA 3799), Bat. 6, case n°15, UFR Sciences, Université de Reims, Champagne-Ardenne, 51687 Reims Cedex 2, France. Abstract—The low frequency noise (LFN) method was used to characterize a two-dimensional electron gas (2DEG) in a double AlGaAs/GaAs/AlGaAs heterojunction from room temperature to cryogenic one. Measurements on noise presented by the power spectral density (PSD) of drain voltage are analyzed as a function for different applied voltages and temperatures in the frequency range from 1 Hz to 100 kHz. PSD can be considered as a sum of different contributions (thermal noise, generation- recombination noise and 1/f noise). The experimental results of the thermal noise versus device length of the sample permitted us to estimate the contribution of the contact noise and the results showed the good quality of contacts. The generation recombination noise is studied and traps responsible for capture and emission of carriers are identified by their activation energy and capture cross-section. I. INTRODUCTION Noise is still considered as a hampering limitation of the device performance for electronic. However it is well accepted as a very sensitive measure of the quality and reliability of electronic devices [1-3]. Furthermore, conduction fluctuations often give information about the scattering process. It soon became clear that a better understanding of the most important failure mechanisms affecting electron devices and systems was required in order to improve their reliability. Among device characterization methods, the low frequency noise is usually used because it is a sensitive and non destructive reliability indicator [2, 3]. High electron mobility heterostructure is an important device for high speed, low noise applications in analog and digital circuits, especially for low temperature applications (e.g. bolometer). This is the reason why we are interested to the study of the low frequency noise at various temperatures and for different applied voltages. The applied voltages were fixed at 0, 50 and 100 mV, and the temperature has been swept from 300 K down to 4 K. Furthermore, we extracted the corner frequencies from a generation-recombination (G-R) noise which has a thermal activated behavior whose activation energy was determined. II. EXPERIMENTAL SETUP AND SAMPLE STRUCTURE In our experiments, we used a sample (see Fig. 1) which was grown on a semi-insulating <100> GaAs substrate by molecular-beam epitaxy (MBE). The AlGaAs/GaAs heterostructure consists of a 10 nm GaAs (n+) cap layer, a 15 nm Al x Ga 1x As layer (x = 19.6 %) followed by a delta doping layer Si δ-doping with a density of 8×10 12 cm 2 . An Al x Ga 1x As layer of 35 nm thick (x = 19.6 %) with a Si δ- planar doping density of 10 12 cm 2 , an Al x Ga 1x As spacer layer of 40 nm, followed by a GaAs well of 20 nm, and an Al x Ga 1-x As (x = 19.6 %) layer. Figure 1. A schematic representation of the studied structure. To create electrical contacts, Ni was deposited by evaporation on the GaAs layer followed by evaporation of Au/Ge eutectic. Two metallic layers made of Ni and Al were then successively deposited. Finally, the samples were heated to about 400 °C to allow Ge to diffuse through GaAs. This diffusion reduces the created depletion layer under metallic contacts. The experimental procedure is well described in [4]. The studied sample is similar to a sheet resistance represented by a GaAs channel with a two-dimensional electron gas (2DEG). In other word, the sample is similar to a HEMT (high electron mobility 2010 International Conference on Design & Technology of Integrated Systems in Nanoscale Era -1- 978-1-4244-6339-8/10/$26.00 ©2010 IEEE