Using vertical capacitance–voltage measurements for fast on‐wafer characterization of epitaxial GaN‐on‐Si material

Abstract

We propose and demonstrate an efficient approach to extract key parameters of GaN‐based 2DEG heterostructures grown on conducting Silicon substrates. The methodology enables an electrical feedback on different epitaxial design or MOCVD growth conditions in a very short‐time frame by means of vertical capacitance–voltage (C–V) measurement on simple gate‐metal top‐electrodes, which are evaporated through a shadow mask. Key parameters such as sheet charge carrier density of the 2DEG‐channel, (AlGaN) barrier thickness between 2DEG and top‐electrode and threshold voltage of 2DEG depletion can be extracted with minimum effort. All respective parameters can be logged across the entire wafer without the need for a sophisticated device process and reveal the lateral (in‐) homogeneity of the wafer material. In addition, this method can be used to mimic the gate‐module of metal–insulator–semiconductor (MIS)‐HEMTs and, therefore, to study different charge‐related properties of the dielectric‐GaN interface or the dielectric layer itself.

Temperature dependent lateral and vertical conduction mechanisms in AlGaN/GaN HEMT on thinned silicon substrate

“…This choice of integration limits results in values for n s which are in good agreement with Hall effect measurements (as discussed later), however this is in disagreement with the integration limits proposed in Ref. 15). Capacitance values measured at vertical biases >−3 V (region III) correspond to the total capacitance consisting of the series combination of the buffer capacitance (as well as underlying layers) and the fully enhanced 2DEG.…”

“…1(a)] feature a gate-metal Schottky contact (not annealed) top-electrode and are used for vertical C-V measurements. 15) The top electrode is circular with a diameter of 600 μm. To allow the vertical characterization of the 2DEG the capacitance of the thin AlGaN barrier C barrier has to dominate the series combination of C barrier and the capacitance of the highly isolating and thick GaN buffer C buffer .…”

“…This is only achieved with an intact AlGaN layer and therefore no mesa isolation is applied to avoid the interruption of the 2DEG. 15) Samples of the type B [see Fig. 1(b)] feature test structures such as scaled 2-finger test-transistors and circular Schottky barrier diodes (SBD) with a diameter of 600 μm.…”