Low-Temperature Activation of Ion-Implanted Boron and Nitrogen Ions in Cd _x Hg_1–x Te Heteroepitaxial Layers

Processes of electrical activation of ion-implanted boron and nitrogen atoms in Cd _x Hg_1–x Te (CMT) heteroepitaxial layers grown by methods of molecular-beam epitaxy (HEL CMT MBE) and liquid-phase epitaxy (LPE CMT) have been investigated; likewise in bulk crystals of CMT with low-temperature annealings under anodic oxide. The possibility has been demonstrated of using anodic oxide as an efficient mask for postimplantation annealings of p-type HEL CMT MBE in the temperature interval Т = 200–250°C without disruption of the composition of the variband layer or alteration of the electrophysical properties of the structure. It has been established that in HEL CMT MBE the efficiency of activation of boron as a slowly diffusing donor impurity is lowered with growth of the dose of the B⁺ ions and is increased by thermal cycling from Т = 77 K to room temperature. Implanted nitrogen, in contrast to boron, is a rapidly diffusing acceptor impurity in CMT, efficiently compensating both radiation donor centers and activated boron. The degree of electrical activation of nitrogen grows substantially upon thermal cycling. It has been shown that the mobility spectrum is an efficient method for monitoring the process of electrical activation of boron in p-type HEL CMT MBE. Mesa photodiodes based on activated boron in p-type HEL CMT MBE with long-wavelength photosensitivity boundary λ_c = 11 μm, prepared here for the first time, had a high maximum value of the product of the differential resistance by the area of the photodiode R _d A = (6 − 8)⋅10² Ω⋅cm², product R ₀ A = 5 − 6 Ω⋅cm² (at zero bias), and a diffusion ledge on the inverse branch of the current-voltage (I–V) characteristic out to a bias voltage of 1.3 V.