The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

Recent research results pertaining to InN, GaN and AlN are reviewed, focusing on the different growth techniques of Group III-nitride crystals and epitaxial films, heterostructures and devices. The chemical and thermal stability of epitaxial nitride films is discussed in relation to the problems of deposition processes and the advantages for applications in high-power and high-temperature devices. The development of growth methods like metalorganic chemical vapour deposition and plasma-induced molecular beam epitaxy has resulted in remarkable improvements in the structural, optical and electrical properties. New developments in precursor chemistry, plasma-based nitrogen sources, substrates, the growth of nucleation layers and selective growth are covered. Deposition conditions and methods used to grow alloys for optical bandgap and lattice engineering are introduced. The review is concluded with a description of recent Group III-nitride semiconductor devices such as bright blue and white light-emitting diodes, the first blue-emitting laser, high-power transistors, and a discussion of further applications in surface acoustic wave devices and sensors.

https://iopscience.iop.org/article/10.1088/0022-3727/31/20/001/pdf

Growth and applications of Group III-nitrides

In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band‐gap semiconductors the most promising ...

Semiconductor ultraviolet detectors

To study the effects of plasma chemistries on etch characteristics and plasma-induced damage to the optical properties, dry etching of ZnO films has been carried out using inductively coupled plasmas of Cl2/Ar, Cl2/H2/Ar, and CH4/H2/Ar. The CH4/H2/Ar chemistry showed a faster etch rate and a better surface morphology than the Cl2-based chemistries. Etched samples in all chemistries showed a substantial decrease in the PL intensity of band-edge luminescence mainly due to the plasma-induced damage. The CH4/H2/Ar chemistry showed the least degradation of the optical properties.

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Dry etching of ZnO films and plasma-induced damage to optical properties

Wide bandgap GaN has long been sought for its applications to blue and UV emitters and high temperature/high power electronic devices. Recent introduction of commercial blue and blue-green LED's have led to a plethora of activity in all three continents into the heterostructures based on GaN and its alloys with AlN and InN. In this review, the status and future prospects of emerging wide bandgap gallium nitride semiconductor devices are discussed. Recent successes in p-doping of GaN and its alloys with InN and AlN, and in n-doping with much reduced background concentrations have paved the way for the design, fabrication, and characterization of devices such as MESFET's, MISFET's, HBT's, LED's, and optically pumped lasers. We discuss the electrical properties of these devices and their drawbacks followed by future prospects. After a short elucidation of materials characteristics of the nitrides, we explore their electrical transport properties in detail. Recent progress in processing such as formation of low-resistance ohmic contacts and etching is also presented. The promising features of quarternaries and double heterostructures in relation to possible current injection lasers, LED's, and photodetectors are also elaborated on. >

Emerging gallium nitride based devices

Inductively coupled plasma (ICP) etch rates for GaN are reported as a function of plasma pressure, plasma chemistry, rf power, and ICP power. Using a Cl2/H2/Ar plasma chemistry, GaN etch rates as high as 6875 A/min are reported. The GaN surface morphology remains smooth over a wide range of plasma conditions as quantified using atomic force microscopy. Several etch conditions yield highly anisotropic profiles with smooth sidewalls. These results have direct application to the fabrication of group‐III nitride etched laser facets.

Inductively coupled plasma etching of GaN

Inductively coupled plasma (ICP) etching of GaAs, GaP, and InP is reported as a function of plasma chemistry, chamber pressure, rf power, and source power. Etches were characterized in terms of rate and anisotropy using scanning electron microscopy, and root-mean-square surface roughness using atomic force microscopy. ICP etch rates were compared to electron cyclotron resonance etch rates for Cl2/Ar, Cl2/N2, BCl3/Ar, and BCl3/N2 plasmas under similar plasma conditions. High GaAs and GaP etch rates (exceeding 1500 nm/min) were obtained in Cl2-based plasmas due to the high concentration of reactive Cl neutrals and ions generated as compared to BCl3-based plasmas. InP etch rates were much slower and independent of plasma chemistry due to the low volatility of the InClx etch products. The surface morphology for all three materials was smooth over a wide range of etch conditions.

High-density plasma etching of compound semiconductors

We have investigated the etch rates, residual lattice damage, surface morphologies, and chemistries of InP, InGaAs, AlInAs, and GaAs plasma etched in electron cyclotron resonance (ECR) CH4/H2/Ar discharges. The etch rates of InP and InGaAs increase linearly with additional rf biasing of the substrate, and are approximately a factor of 2 faster than for GaAs. Under our conditions the etch rate of Al0.52Ga0.48As is very low (∼25 A min−1) even for the addition of 100 V rf bias. In all of these materials the residual damage layer remaining after dry etching is very shallow (∼20 A) as evidenced from Schottky barrier height and photoluminescence measurements combined with wet chemical etching. InP shows significant P depletion with the addition of rf biasing during the ECR etching while GaAs retains a near‐stoichiometric surface. Hydrogen passivation of shallow donors in n‐type GaAs occurs to a depth of ∼3000 A during exposure to the CH4/H2/Ar discharge for long periods (60 min). The surface morphologies in the...

Plasma etching of III–V semiconductors in CH4/H2/Ar electron cyclotron resonance discharges

Smooth, anisotropic dry etching of InN, AlN and GaN layers is demonstrated using low-pressure (1-30 mTorr) CH4/H2/Ar or Cl2/H2 ECR discharges with additional DC biasing of the sample. The etch rates are in the range 100-400 AA min-1 at 1 mTorr and -150 V DC for Cl2/H2, while higher biases are needed to initiate etching in CH4/H2/H discharges. The presence of hydrogen in the gas chemistries is necessary to facilitate equi-rate removal of the group III and nitrogen etch products, leading to smooth surface morphologies.

https://iopscience.iop.org/article/10.1088/0268-1242/8/2/026/pdf

Dry etching of thin-film InN, AlN and GaN

Dry etching of GaN in Cl2/H2/CH4/Ar has been compared using electron cyclotron resonance (ECR), inductively coupled plasma (ICP), and reactive ion etch (RIE) systems. GaN etch rates and surface morphology were obtained as a function of RF power, and showed significant improvements under high density plasma conditions.

C. Constantine

Papers

Inductively coupled plasma etching of GaN

High-density plasma etching of compound semiconductors

Plasma etching of III–V semiconductors in CH4/H2/Ar electron cyclotron resonance discharges

Dry etching of thin-film InN, AlN and GaN

Comparison of dry etch techniques for gan