Application of ZnO to Passivate the GaN-based Device Structures (original) (raw)
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Materials Science in Semiconductor Processing, 2018
Zn acceptor/Ge donor (Zn/Ge)-codoped GaN films with different Zn contents have been deposited on Si substrates at 300°C and at 90-150 W by RF reactive sputtering technique with cermet targets at the composition atomic ratios of Zn:Ge:(Ga+GaN) at x:0.03:(0.97-x) with x = 0, 0.03, 0.06, and 0.09 and Ga:GaN = 3:7. The films made with such targets were presented in an abbreviated symbol of Zn-x-GeGaN at x = 0, 0.03, 0.06, and 0.09. The morphology, structure, electrical properties, optical property, and hetero-junction diode devices involved in the Zn-x-GeGaN films were thoroughly investigated. The systematic Zn increment into the n-type Zn-0-GeGaN through property evaluation provides the supporting information in studying solid solutioning. Zn-x-GeGaN films converted into p-type semiconductor at x = 0.06 and 0.09. The values of bandgap were in the range of 2.87-3.17 eV with the lower value for the higher Zn content in Zn-x-GeGaN films. The higher RF power led to the faster growth, highly deficient in nitrogen, and a higher Zn atom ratio in the deposited film. The 120Wdeposited Zn-0.06-GeGaN film had hole concentration of 7.21 × 10 16 cm −3 , hole mobility of 39.1 cm 2 V −1 s −1 , and the electrical conductivity of 0.45 S/cm.
A comparative study of surface passivation on AlGaN/GaN HEMTs
Solid-state Electronics, 2002
Using a Si 3 N 4 layer as passivation layer, effects of surface passivation on device performances have been investigated. After passivation, devices exhibited better pinch-off characteristics and lower gate leakage current. For a device with a gate-length of 0.25 lm, the I dss increased from 791 to 812.2 mA/mm and the peak extrinsic transconductance increased from 207.2 to 220.9 mS/mm. The f T and f MAX values decreased from 53 and 102.5 to 45.9 and 90.5 GHz, respectively, due to the increase of parasitic capacitances. Microwave noise measurements showed that devices exhibited 0:2-0:25 dB increase in minimum noise figure (NF min ) after passivation. Ó
Passivation of Surface and Interface States in AlGaN/GaN HEMT Structures by Annealing
Journal of Electronic Materials, 2007
The Ni/AlGaN interfaces in AlGaN/GaN Schottky diodes were investigated to explore the physical origin of post-annealing effects using electron beam induced current (EBIC), current-voltage (I-V) characteristics, and X-ray photoelectron spectroscopy (XPS). The EBIC images of the annealed diodes showed that the post-annealing process reduces electrically active states at the Schottky metal/AlGaN interfaces, leading to improvement of diode performance, for example a decrease in reverse leakage current and an increase in Schottky barrier heights. Pulsed I-V characteristics indicate the Fermi level is up-shifted after annealing, resulting in a larger sheet carrier density at the AlGaN/GaN interface. Unintentional oxidation of the free AlGaN surface during the post-annealing process, revealed by XPS analysis, may prevent electron trapping near the drain-side of the gate edges. We suggest that the post-annealing process under an optimized conditions can be an effective way of passivating AlGaN/GaN heterojunction field-effect transistors.
Effect of Surface Passivation on the Electrical Characteristics of Nanoscale AlGaN/GaN HEMT
IOP Conference Series: Materials Science and Engineering
In this paper, we present the effect of passivation layer on the electrical characteristics of AlGaN/GaN HEMT. The energy band diagram, drain current voltage characteristics, transconductance and cut off frequency was calculated for both long channel and short channel devices. It was found that the electrical characteristics of the device improve with the introduction of high K dielectric in the passivation layer. The results obtained agree well with the data available in literature.
ZnO thin film templates for GaN-based devices
2005
GaN-based optoelectronic devices are plagued by a tendency to non-radiative transitions linked to defects in the active layers. This problem has its origin in (1) intrinsic factors such as GaN's relatively low exciton binding energy (~24meV) and (2) extrinsic factors including the poor availability of native substrates good enough to significantly suppress the defect density. Indeed, the quality and availability of large-area bulk GaN substrates is currently considered a key problem for the continuing development of improved GaN-based devices. Since development of bulk GaN substrates of suitable quality has proven very difficult, a considerable amount of effort is also being directed towards the development of alternative substrates which offer advantages compared to those in widespread use (c-sapphire and 6H SiC). ZnO is promising as a substrate material for GaN because it has the same wurtzite structure and a relatively small lattice mismatch (~1.8%). In this paper, we discuss use of ZnO thin films as templates for GaN based LED.
ALD-grown Ultrathin AlN Film for Passivation of AlGaN/GaN HEMTs
An effective passivation technique for AlGaN/GaN HEMTs is presented. This technique features AlN ultrathin film grown by plasma enhanced atomic layer deposition (ALD). With in-situ remote plasma pretreatments prior to the AlN deposition, atomically sharp interface between ALD-AlN and III-nitride has been obtained. Effective current collapse suppression and dynamic ON-resistance reduction are demonstrated in the ALD-AlN passivated AlGaN/GaN HEMTs under high drain bias switching conditions.
Effect of surface passivation on performance of AlGaN/GaN/Si HEMTs
Solid-State Electronics, 2003
Performance of intentionally undoped and doped AlGaN/GaN/Si high electron mobility transistors (HEMTs) before and after passivation with SiO 2 and Si 3 N 4 is investigated. Hall effect measurements show higher impact of Si 3 N 4 than SiO 2 passivation on the carrier concentration increase in the channel. Improvements in DC performance of HEMTs after passivation with SiO 2 and Si 3 N 4 correspond to the changes in sheet carrier concentration. Small signal microwave characterisation shows a decrease (from 18.6 to 9 GHz) and an increase (from 18.4 to 28.8 GHz) of the current gain cut off frequency after SiO 2 and Si 3 N 4 passivation, respectively. Similar effect of passivation is found in microwave power changes--only about a half of the power is obtained after SiO 2 passivation but more than doubled power results from Si 3 N 4 passivation, measured at 2 GHz. Higher density of interface states for SiO 2 than Si 3 N 4 passivation is supposed to be responsible for these effects. However, for an optimal design of GaN-based power devices additional studies related to the interface between a passivation layer and GaN are needed.
MOCVD of ZnO thin films for potential use as compliant layers for GaN on Si
Journal of Crystal Growth, 2008
This paper explores the use of nanostructured zinc oxide (ZnO) films as a compliant buffer layer for the growth of gallium nitride (GaN) on silicon substrates. Thin films of ZnO have been deposited on silicon (1 1 1) substrates by liquid injection metalorganic chemical vapour deposition (MOCVD) using dimethyl zinc-tetrahydrofuran adduct and oxygen. The use of the adduct complex avoids prereaction between the dialkyl zinc complex and oxygen which has been observed elsewhere. ZnO films deposited by this method were stoichiometric and of high purity, with no detectable carbon contamination. Films were deposited over a temperature range 350-550 1C, and exhibited a nanowire-like morphology. Subsequent deposition of GaN layers grown by molecular beam epitaxy (MBE) on the ZnO film resulted in the transformation of the nanowires to gallium oxide, accompanied by virtually complete removal of zinc from the layer. A heteroepitaxially oriented (c-axis) GaN/gallium oxide/silicon structure was produced after the nitride deposition which consisted of characteristic columnar GaN with the GaN[0 0 0 1]||Si [1 1 1]. Selective area electron diffraction of the by-product oxide interlayer showed a polycrystalline-like behaviour that gave rise to a random azimuthal distribution of the GaN grains. r
Journal of Electronic Materials, 2010
We investigated the properties of indium-doped zinc oxide layers grown by metalorganic chemical vapor deposition on semi-insulating GaN(0001) templates. Specular and transparent films were grown with n-type carrier concentrations up to 1.82 9 10 19 cm À3 as determined by Hall measurements, and all In-doped films had carrier concentrations significantly higher than that of a comparable undoped film. For low In flows, the carrier concentration increased accordingly with trimethyl-indium (TMIn) flow until a maximum carrier concentration of 1.82 9 10 19 cm À3 was realized. For higher In flows, the carrier concentration decreased with increasing TMIn flow rate. Sheet resistance as low as 185 X/sq was achieved for the In-doped films, which is a significant decrease from that of a comparable undoped ZnO film. Our n-type doping studies show that In is an effective dopant for controlling the n-type conductivity of ZnO.