Deep level investigation of p-type GaN using a simple photocurrent technique

Abstract

Effects of interface states and temperature on the C -V behavior of metal/insulator/AlGaN/GaN heterostructure capacitorsThe deep level spectrum of p-type GaN was investigated using time-resolved photocurrent spectroscopy. The spectral dependence of the optical cross section for hole photoemission from a deep level was determined from the initial value of the photocurrent transient. Unlike other implementations of photocurrent, the present method does not require multiple excitation sources or determination of the optical emission rate. A deep level was observed at E v + 1.84 eV, where E v is the valence band maximum, with a Franck-Condon shift of 0.25 eV. A bias-dependent component of the photocurrent, possibly due to metal-semiconductor interface states, complicated the steady-state response but did not affect the measured spectrum for the E v + 1.84 eV deep level. This photocurrent method is expected to be readily extended to materials with very deep dopants, such as p-type AlGaN, for which many other deep level spectroscopy techniques are unsuited.

Quantitative and Depth-Resolved Investigation of Deep-Level Defects in InGaN/GaN Heterostructures

“…21 However, the large calculated formation energies of these native defects in GaN 21 suggest that extrinsic defects are a more likely source for the E v + 1.85 and E v + 2.51 In 0.02 Ga 0.98 N defect levels. The energy of the E v + 1.85 eV defect level is similar to the ''OLP1'' deep level reported in MOCVD-grown GaN:Mg, 22,23 suggesting a common physical source such as a threading dislocation, carbon or oxygen impurities, or even Mg diffused into the UID In 0.02 Ga 0.98 N from the adjacent p-GaN region. Based on the 3.36 eV bandgap of the In 0.02-Ga 0.98 N UL, the E v + 3.30 eV (E c À 0.06 eV) level is likely due to the nitrogen vacancy, which has been assigned to a shallow donor level 0.07 eV from E c .…”

Electrical characteristics of Mg-doped p-GaN treated with the electrochemical potentiostatic activation method

“…For example, based on the measured N values before and after EPA treatment (at 7 V), the barrier width (W) was calculated to be 49.6 nm and 41.0 nm, respectively, according to W = [(2e s /N)(U b À V p )] 1/2 , where e s is the dielectric constant of GaN, qU b is the Schottky barrier height, and V p is the energy difference between the Fermi level (E F ) and the valence band (E V ). Here, qU b was estimated using the relation of qU b = qu + E D0 , where E D0 = 1.84 eV [17,18]. Therefore, the improved ohmic contact was due to reduced barrier width associated with an increase in hole carriers, as depicted in the inset of Fig.…”

Characterization of hole traps in MOVPE-grown p-type GaN layers using low-frequency capacitance deep-level transient spectroscopy

“…[10][11][12] To obtain a p-GaN-based Schottky diode, both electrodes are formed for a p-GaN layer because a p-GaN substrate has not been available until now; this reduces the testable doping range. Moreover, such diodes usually suffer from leakage current and/or series resistance, [13][14][15][16] leading to quantitative inaccuracy. Reference 16 provided an answer to this problem by using a p + /p − /n + structure grown by NH 3 -based molecular beam epitaxy.…”