Amino acids have both acidic and basic group(amine) which lead to the formation of zwitterions and make them dipolar compounds. Due to this property, they form strong molecular bonds themselves and also with water. This result high melting point and good solubility in water as compared to haloacids.
Halo acids doesn't exhibit the property of dipolar compounds. Only carboxyl group of haloacid is involved in H-bonding, not the halogen atom. That's why they have low melting points and less solubility than amino acids.