Properties of AlN/GaN Heterostructures Grown at Low Growth Temperatures with Ammonia and Dimethylhydrazine

The integration of different electronic materials systems together has gained increasing interest in recent years, with the III-nitrides being a favorable choice for a variety of electronic applications. To increase flexibility in integration options, growing nitrides material directly on semi-processed wafers would be advantageous, necessitating low temperature (LT) growth schemes. In this work, the growth of AlN and GaN was conducted via metalorganic chemical vapor deposition (MOCVD) using both NH3 and DMHy as N-precursors. The relationships between growth rate versus temperature were determined within the range of 300 to 550 °C. The growth of AlN/GaN heterostructures was also investigated herein, employing flow modulation epitaxy MOCVD at 550 °C. Subsequent samples were studied via atomic force microscopy, X-ray diffraction, TEM, and Hall measurements. Two-dimensional electron gases were found in samples where the LT AlN layer was grown with NH3, with one sample showing high electron mobility and sheet charge of 540 cm2/V∙s and 3.76 × 1013 cm−2, respectively. Inserting a LT GaN layer under the LT AlN layer caused the mobility and charge to marginally decrease while still maintaining sufficiently high values. This sets the groundwork towards use of LT nitrides MOCVD in future electronic devices integrating III-nitrides with other materials.

Revealing quantum effects in highly conductive δ-layer systems

Thin, high-density layers of dopants in semiconductors, known as δ-layer systems, have recently attracted attention as a platform for exploration of the future quantum and classical computing when patterned in plane with atomic precision. However, there are many aspects of the conductive properties of these systems that are still unknown. Here we present an open-system quantum transport treatment to investigate the local density of electron states and the conductive properties of the δ-layer systems. A successful application of this treatment to phosphorous δ-layer in silicon both explains the origin of recently-observed shallow sub-bands and reproduces the sheet resistance values measured by different experimental groups. Further analysis reveals two main quantum-mechanical effects: 1) the existence of spatially distinct layers of free electrons with different average energies; 2) significant dependence of sheet resistance on the δ-layer thickness for a fixed sheet charge density.

Analytical Model Development for Unified 2D Electron Gas Sheet Charge Density of AlInN/GaN MOSHEMT

We have developed a unified analytical model for computation of 2D electron gas sheet charge density in AlInN/GaN metal-oxide-semiconductor high electron mobility transistor device structure. This model has been developed by incorporating the variation in lowest three energy sub-bands and Fermi level energy in the quantum-well with respect to gate voltage. We noticed that the dependency of lowest sub-band energy with Fermi energy having two fields, which are the lowest sub-band energy is greater and lesser than the Fermi level energy. According to these two fields, we have developed the fermi energy and sheet charge density expressions in each field. By combining each field of the models, developed a unified 2D electron gas sheet charge density model. The Fermi level and sheet charge density are interdependent in the model development. The developed model results are compared with TCAD simulation results and obtain a good consistency between them. This model is fitted to other metal-oxide-semiconductor high electron mobility transistor devices also with modifications in related physical values.

Comparative Study of the Characteristics in Strained AlxInyGa(1-x-y)N/InGaN and AlxInyGa(1-x-y)N/GaN Heterostructures

The paper emphasized on different characteristics AlInGaN/InGaN and AlInGaN/GaN heterostructures for enhancing the device performance. Effect of changing mole fraction in bandgap, strain, polarization have been investigated. Amount of sheet charge density created on the heterointerfaces of AlInGaN /InGaN and AlInGaN/GaN heterostructures have been calculated. It has been observed that with the increment of Indium mole fraction and the decrement of Aluminium mole fraction, the total polarization increases hence larger 2DEG and sheet charge density is created.